First of all, I would like to point out that this question should be able to be answered without getting into matters of the validity of Luke. Unfortunately, the question itself expands past the basic question to inquire about Luke's account, though this is an entirely separate question than the main title question given.

Current answers have swapped the main question and sub-question and seem to make the validity of Luke their starting point. It is my intention to first address the question of the procedure for a census. I will then proceed in my second section to address the issues in Luke (which should be an entirely separate question and answer but I will put two answers in one). I will also address the many misunderstandings, incorrect assumptions and faulty logic provided in the other answers about Luke and Matthew's accounts.

Roman Census

We should make it clear that we have little to no information for how the Romans actually performed their censuses. We do have some information on the censuses themselves, their time and results, many times one without the other (a year with no result or a result with no year). But while we have details on how the Romans did it very early on, with ceremony, centuries later and for censuses in foreign provinces we have little information.

Romans began having censuses as far back as the 5th century BCE under Servius Tullius, king of Rome. Wiki

the following passage of Cicero:...can be translated as: "The Censors are to determine the generations, origins, families, and properties of the people; they are to (watch over/protect) the city's temples, roads, waters, treasury, and taxes; they are to divide the people into three parts; next, they are to (allow/approve) the properties, generations, and ranks [of the people]; ..." Wiki

This is referring to earlier censuses of the Romans themselves (Cicero lived in the early first century 106-43 BCE), but it gives us some insight into the far reaching purposes behind the census.

After a citizen had stated his name, age, family, etc., he then had to give an account of all his property, so far as it was subject to the census. Wiki

Again, we can see the emphasis not simply on wealth, but on the value of property.

By the time of the birth of Jesus, the ceremony of the door to door census was long gone. Certainly not outside Rome itself among the provinces. Wiki

A census was sometimes taken in the provinces, even under the republic. The Emperor sent into the provinces special officers called Censitores to take the census; but the duty was sometimes discharged by the Imperial legati. The Censitores were assisted by subordinate officers, called Censuales, who made out the lists, &c. In Rome, the census was still taken under the empire, but the old ceremonies connected with it were no longer performed, and the ceremony of the lustration was not performed after the time of Vespasian.[Died in 79]

A census edict for Roman Egypt in 104 CE tells us three things:1

1. That it required people to return to their homes.
2. That "registration" was involved.
3. That the prefect appointed a military commander.

All three of these may apply directly to Luke's account as we will see below.

After many of years of civil war in the first century BCE, the practice of regular census and censor appointments had been neglected. However, Augustus changed that,

During the civil wars which followed soon afterwards, no censors were elected; it was only after a long interval that they were again appointed, namely in 22 BC, when Augustus caused Lucius Munatius Plancus and Aemilius Lepidus Paullus to fill the office.

Compare that to Luke 2:1 (ESV)

In those days a decree went out from Caesar Augustus that all the world should be registered.

In the wider historical context, it seems clear that this decree by Augustus in Luke does not necessarily refer to a singular massive census, but to the reinstatement of regular censuses which had fallen out of practice. At the same time it does give us cause for the specific census by Quirinius mentioned in Luke 2:2. After all, if it was one massive "Augustus' Census" then why would Luke need to specify any further?

Luke's language of "in those days" is idiomatic of an era or period, not of literal days leading up to his account. It may have been Luke's attempt to borrow language from other historical narratives in the Hebrew Torah. See Genesis 6:4, Judges 17:6, Judges 20:27 for cases where "in those days" clearly involves years, not days. It can also mean literal days of course, but such a literal requirement is unwarranted.

Ultimately we can conclude that:

1. Augustus' decree can see in a larger historical context
2. Registration of some form would indeed require one return to one's own town.

Do note here that in the Jewish culture, the man's family line takes precedence over the woman's. So the registration would have been for Joseph's home, not Mary's.

Luke's account

Quirinius

Luke 2:2 ESV

This was the first registration when Quirinius was governor of Syria.

If we suppose that Quirinius was taking over the entire province of Syria in the common date of AD 6, he must have held several lesser positions prior in order to be eligible for such a position. 2 The title of Hegemon given to Quirinius here does not demand he be Legatus of the entire province. Perhaps he was serving a lesser position in the area at the time and was involved in the census. His later elevation to Legatus would make him a known name for Luke to reference. At the same time, it would then make sense for Luke to stipulate that this was the first registration by Quirinius.

Furthermore, we have an inscription which speaks of an unnamed official who received many commendations to accompany military success, was proconsul of Asia and was governor of Syria twice.12 Unfortunately, the name of this official is lost, but it very well may have been Quirinius as he fits many of the descriptions. He was well liked by Augustus, had many military successes and was one of four known men to be governor of Syria around that time. There is a time frame unaccounted for from 4-1 BCE which would likely be the duration of this second term. 3 This just so happens to be the prime time frame for the birth of Christ. (Readers who object to this based on Herod's death in 4 BCE should consider that such a date may be a typesetting mistake and the previously traditional date of 1 BCE may be accepted.) 4

Not only that, but we have Roman records placing Quirinius in Asia minor (Rhodes and Armenia) during this time as a military commander, 14 and another record showing that he appointed one of his own men to do a census as far south as Apamea (in Syria). 13 This matches with what we read in the earlier section that military commanders were often assigned this duty. That he also commanded or oversaw a census of Judea with Herod at this time is not beyond reason.

But what about Josephus' date of 6 CE? There is good reason to think that Josephus may have been incorrect to initially accepted the date of 6 CE and later, despite its inconsistancies, continued to support it. In his article JOSEPHUS MISDATED THE CENSUS OF QUIRINIUS, John H. Rhoads makes a compelling argument based on internal evidence from Josephus' writings for the governorship, and census, of Quirinius during the reign of Herod the Great. 6 If Rhoads is correct, a number of these issues would be resolved.

Joseph's return to Bethlehem

Luke 2:3,4

3 And all went to be registered, each to his own town.

4 And Joseph also went up from Galilee, from the town of Nazareth, to Judea, to the city of David, which is called Bethlehem, because he was of the house and lineage of David...

Returning to the main question, as we saw in my earlier section, Joseph would have had to return to Bethlehem for a number of possible reasons. The first being that he may have been the primary representative of his family's holdings in Bethlehem. The second being that he was born there (not just some long dead family from there, but Joseph himself). And lastly, the strong possibility that he resided there himself. It was his own town.

Note that this does not mean that Joseph did not "live" in Nazareth as well. Many people have official residencies in one place, but actually live most of the time elsewhere. This is common when it is connected with family, property, or nationality, all of which could apply to Joseph and Bethlehem. I am reminded of a few Canadians I know who live much of the year in the US but maintain their Canadian citizenship. To do so they must return to Canada for a portion of the year. Joseph also would have been legally obliged to return to Bethlehem for a census.

But if Joseph lived there, why did they leave from Galilee?

Quite simply, they were in Nazareth because Mary was from Galilee. Luke 1:26, 27 says,

26 In the sixth month the angel Gabriel was sent from God to a city of Galilee named Nazareth,

27to a virgin betrothed to a man whose name was Joseph, of the house of David. And the virgin’s name was Mary.

Joseph and Mary had only just consummated their marriage, as wedding feasts typically happened in the fall and at the bride's home.7

In Matthew's testimony we read that Joseph learned of Mary's pregnancy during their betrothal period (the roughly year between "engagement" and "consummation") and was considering a quiet divorce/annullment. But after the Angel's visit, Joseph decided to take her as his wife anyway, meaning Mary was likely at least her second trimester by then if Jesus was born between December-February. After the wedding feast the groom would take his new bride home. But considering Mary's condition and the distance to Bethlehem from Nazareth, it is reasonable they did not leave immediately. Perhaps the child was late and they had expected him before they had to travel. Perhaps they needed to wait for spring and the roads to be repaired? We do not know.

Also, we see in Matthew that the family stayed and lived in Bethlehem for up to as many as two years after Jesus was born. Perhaps this was not planned and they just stuck around while Jesus was an infant with Joseph's family around and ended up staying. Or perhaps this was where Joseph had planned to live with his family all along. It is curious to see that after their return from exile to Egypt their first instinct is to return to Bethlehem! It is only because of Archelaus they do not. And so they stay out of Judea and go to Galilee, to Nazareth. Nothing could be more natural, as that was Mary's home town!

So we see that there is nothing unusual about Joseph returning to Bethlehem. There are numerous explanations that fit the chronology and the details given by both Matthew and Luke.

Luke and Matthew do not contradict each other. They certainly focus on different details, but all narration does. All narration also includes time compression, which is how Luke can skip from the Temple to moving to Nazareth while Matthew records a few years worth of events during that time.

Luke includes details about Jesus as a 12 year old, but Matthew does not. Should we then conclude that either Jesus was never a 12 year old or Matthew is wrong? This is clearly not logical! And yet it is the exact same logic used in many criticisms. We would not have a complete picture without both witnesses.

The only real argument, such as the other answers here, that critics have of Luke and Matthew have is an Argument from Silence.

Claiming that we, 2000 years later with limited records and no first or second hand knowledge, know more about the details around the census than Luke did more than 1900 years ago (roughly 70 years later) makes even less sense than a teenager doing some internet research on the Nazi Holocaust (not even 70 years ago) and concluding it was a misunderstanding. 9

I am not necessarily arguing for any one set of the possible solutions I have given. So I understand it may seem confusing when I give multiple possibilities. My objective is to make the readers aware that there are other options besides going out of our way to find things to criticize. I am arguing for a position of caution, of awareness of our ignorance.

Addressing Objections

In (SERIOUS PROBLEMS WITH LUKE'S CENSUS)10 the author, N. F. Gier, makes a number of false assumptions and then bases much of his arguments on them.

There is no record of Caesar Augustus' decree that "all the world should be enrolled" (Lk. 2:1). The Romans kept extremely detailed records of such events.

Such a reading of Luke 2:1 would make even the strongest Literalist interpreter cringe. As I showed at the beginning, Luke's phrase "in those days" is idiomatic for a much larger range of years and could easily include Augustus' initial restart of the census program in 22 BCE.

But an Egyptian papyrus recording a census in 104 C.E. explicitly states that "since registration by household is imminent, it is necessary to notify all who for any reason are absent from their districts to return to their own homes that they may carry out the ordinary business of registration...."

Geir only quotes Luke, and selectively at that, when it helps his case. Luke 2:3

And all went to be registered, each to his own town.

Geir ignores that fact that Luke's language here is identical to the evidence he is presenting against him. If Joseph's home was Bethlehem this objection crumbles. So Geir makes an effort to disqualify the possibility of Bethlehem being Joseph's home by quoting Luke 2:39.

And when they had performed everything according to the Law of the Lord, they returned into Galilee, to their own town of Nazareth.

Luke skips over Matthew's account of staying in Bethlehem for a time and then fleeing to Egypt. This claim of Nazareth being their "own town" is no stronger than the claim of Luke 2:3 that Bethlehem was Joseph's "own town". One can only suspect why Geir takes 2:39 as conclusive but not 2:3. Also, as was said, Mary's own home was in fact Nazareth, and after a couple of years it became their family's home indefinitely. Looking back in history, it would be natural to refer to Nazareth as their home, because it was, why would Luke need to qualify whether it was both their homes in that year?

Geir attempts to support his dismissal of Luke by saying,

Unlike Matthew, who does not mention a census nor Nazareth as Mary and Joseph's home, Luke describes Nazareth as "their own city" (Lk. 2:39). If the rules of this Egyptian census applied to Palestine, then Joseph and Mary should have stayed in Nazareth to be enrolled.

He claims this despite the fact that Matthew does indeed give Nazareth as the eventual home of Mary and Joseph, after their exile, attempted return to Bethlehem first, but fleeing to Nazareth. (Matt 2:23 "And he went and lived in a city called Nazareth")

Geir continues to display his poor biblical hermeneutics when he cites John 7:41 as proof John did not think Jesus was born in Bethlehem. John is actually recounting what some of the people were saying about Jesus. That they thought of him as from Galilee while knowing the messiah should be from Bethlehem does not indicate John did not know Jesus was born in Bethlehem. It means John was recounting the words of people who did not. That's all. As it says in 7:43 "So there was a division among the people over him." What it does indicate is that Jesus had been living in Nazareth since he was around 2 years old. My mother was born and lived in Puerto Rico for a few years. She is not "from" Puerto Rico. If you ask her she will say she's from a town in California, which is where she grew up.

The scholarly consensus is almost unanimous on this point: Luke is simply wrong. There are a number of reasons why the account provided by Luke cannot be taken seriously; these reasons include contradictions between Luke and the external historical evidence, Luke's obvious misunderstanding of how censuses were conducted, Luke's misunderstanding of geographical and political issues, and simple logic.

Contradictions Between Luke and the Historical Record:

[Jesus was born] In the days of Herod, king of Judaea...
(Luke 1:5)

Emperor Augustus that all the world should be registered. This was the first registration and was taken while Quirinius was governor of Syria. All went to their own towns to be registered. Joseph also went from the town of Nazareth in Galilee to Judaea, to the city of David called Bethlehem, because he was descended from the house and family of David. He went to be registered with Mary, to whom he was engaged and who was expecting a child.
(Luke 2:1–7)

The first problem with this account is that it claims that the reigns of Herod in Judaea, Quirinius in Syria, and Augustus in Rome coincided. In reality, they did not. Herod died in the year 4 CE, and was succeeded by his son Archelaus. Archelaus proved to be an incompetent and brutal King, and the Roman authorities quickly removed him from office in the interest of preventing unrest. In the year 6 CE, therefore, Archelaus was deposed, and Judaea became a province of the Roman Empire, under direct control of a proconsul, overseen by the Governor of Syria, who was, at that time, Quirinius.

When Judaea was made a province, the Emperor ordered Quirinius to conduct a census for the purpose of taxation. The historical record, Luke notwithstanding, shows that the census occurred in the same year Archelaus was deposed, 6 CE, two years after Herod's death.

Luke's Misunderstanding of Geographical and Political Issues:

Luke claims that the census occurred in Judaea, and that Joseph was required to leave Nazareth and go to Bethlehem to be registered for taxation. This is a significant problem, because Nazareth is in Galilee, not Judaea. When Judaea became a province of the Roman Empire, Galilee remained unaffected by the annexation, as a semiautonomous client state. From 4 CE to 39 CE, Galilee was ruled by Herod Antipas, the son of Herod the Great; he was deposed by Emperor Caligula in 39, and Galilee was incorporated into Judaea in the year 44 CE, a few years after Jesus' death.

This brings us to the point: A census in Judaea would have no bearing on Joseph and Mary, who lived in Galilee. Quirinius' jurisdiction ended at the border between Galilee and Judaea, and Herod Antipas had been ruling Galilee for two years prior to the annexation of Judaea as a province of Rome.

Luke's Misunderstanding of Censuses:

The idea that a census would require that people travel to their ancestral home towns is patently absurd. If we imagine how this would affect commerce, trade, communications, and the maintenance of law and order, it becomes absolutely clear that no such requirements existed.

The Roman Empire spanned the entire Mediterranean region, and was inhabited by some 60 million people. The road system was an amazing feat of engineering, but it simply couldn't handle 60 million people simultaneously traveling all over the empire at once. The roads would become clogged almost immediately, and people would try to circumvent the congestion by walking off road, trampling fields of crops, knocking down fences, scattering herds and flocks, and so on. The logistical problems with illiterate peasants trying to figure out where they were supposed to go would be an additional complication.

Imagine a system of taxation based on people returning to their ancestral homes, going back a thousand years in the case of Joseph. By this time the Jews were spread out all over the known world. Can we seriously believe that the Romans would have required them to come back to Palestine, carrying everything they owned? How would the tax officials have assessed their land? In The Rise of Christianity the former Bishop E. W. Barnes remarks: "The Romans were a practical race, skilled in the art of government. It is incredible that they should have taken a census according to such a fantastic system. If any such census had been taken, the dislocation to which it would have led would have been world-wide. Roman historians would not have failed to record it."
- Serious Problems With Luke's Census

On a more fundamental level, making people travel away from home in order to conduct a census for the purpose of tax assessment is illogical and counterproductive. The whole idea of such a census is to evaluate how much property each person owns, and for the vast majority of people in the Roman Empire, the only property they owned was their home, the land on which the home was located, and the livestock they tended for sustenance.

The last, but perhaps the most striking, problem with Luke's account is that he claims Joseph had to go to Bethlehem because of his ancestral connection to David. According to the genealogies of Jesus provided by Matthew and Luke, Joseph and David were separated by something like 42 generations, and about 1,000 years of history. The notion that someone(especially someone who who was almost certainly illiterate and uneducated) would have to trace their ancestry back 42 generations and 1,000 years is simply absurd. The vast majority of people today couldn't do this, despite being literate and having access to centuries worth of government records, much of which are available online. I myself have struggled to find my ancestral roots further back than a few generations.

Thus, if you wanted to determine how much each person should be taxed, the last thing you'd want to do is make them leave their homes. Everything you need to assess is in and around the home.

How Censuses Were Actually Conducted:

This part of the story is the easiest to explain. A census was carried out by census takers traveling from town to town, stopping at each house, recording the relevant data (e.g., the name of the head of household, extent of landholdings, number of livestock, acreage of crop land and yields, number of dependents, and perhaps some other information). The whole point of the undertaking was to determine how much each household owed in taxes.

After a citizen had stated his name, age, family, etc., he then had to give an account of all his property, so far as it was subject to the census. Only such things were liable to the census (censui censendo) as were property according to the Quiritarian law. At first, each citizen appears to have merely given the value of his whole property in general without entering into details; but it soon became the practice to give a minute specification of each article, as well as the general value of the whole.

Land formed the most important article of the census, but public land, the possession of which only belonged to a citizen, was excluded as not being Quiritarian property. If we may judge from the practice of the imperial period, it was the custom to give a most minute specification of all such land as a citizen held according to the Quiritarian law. He had to state the name and location of the land, and to specify what portion of it was arable, what meadow, what vineyard, and what olive-ground: and of the land thus described, he had to give his assessment of its value.

Slaves and cattle formed the next most important item. The censors also possessed the right of calling for a return of such objects as had not usually been given in, such as clothing, jewels, and carriages. It has been doubted by some modern writers whether the censors possessed the power of setting a higher valuation on the property than the citizens themselves gave, but when we recollect the discretionary nature of the censors' powers, and the necessity almost that existed, in order to prevent fraud, that the right of making a surcharge should be vested in somebody's hands, we can hardly doubt that the censors had this power. It is moreover expressly stated that on one occasion they made an extravagant surcharge on articles of luxury; and even if they did not enter in their books the property of a person at a higher value than he returned it, they accomplished the same end by compelling him to pay a tax upon the property at a higher rate than others. The tax was usually one per thousand upon the property entered in the books of the censors, but on one occasion the censors compelled a person to pay eight per thousand as a punishment.
- Wikipedia

And:

In Josephus' account of the census in 6 C.E., he explicitly states that those people taxed were assessed of their possessions, including lands and livestock. In other words, the census takers were also the tax assessors. In Egypt these tax assessors went from house to house in order to perform their duties. With this in mind, let us look at a crucial error in Luke's account. Luke has Joseph and Mary making a three-day journey away from their home in Nazareth to register in their alleged ancestral home Bethlehem. But an Egyptian papyrus recording a census in 104 C.E. explicitly states that "since registration by household is imminent, it is necessary to notify all who for any reason are absent from their districts to return to their own homes that they may carry out the ordinary business of registration...."6 Unlike Matthew, who does not mention a census nor Nazareth as Mary and Joseph's home, Luke describes Nazareth as "their own city" (Lk. 2:39). If the rules of this Egyptian census applied to Palestine, then Joseph and Mary should have stayed in Nazareth to be enrolled.
- Serious Problems With Luke's Census

Why Luke Wrote the Account The Way He Did:

Luke was trying to make Jesus' life story conform to the expectations regarding the Jewish Messiah. The prophets had predicted that the messiah would be born of the House of David. David's place of birth is traditionally named as Bethlehem. Thus, Luke needed Jesus to be born in Bethlehem. This was a problem, because it was common knowledge that Jesus was known as "Jesus of Nazareth".

So what’s going on here? What’s going on is that both Matthew and Luke want Jesus to be born in Bethlehem even though they both know that he came from Nazareth. Both accounts are filled with implausibilities on their own score (a star leading “wise men” to the east – they wouldn’t be very wise if they thought that a star could lead them in a straight line anywhere — and stopping over a house; a census of the entire Roman world that could not have happened); and they contradict each other up and down the map.

My view is that neither story is historical, but that both have an ultimate objective to explain how Jesus could be the messiah if he was from Nazareth instead of Bethlehem. So they (or their sources) came up with stories to get him born in Bethlehem. These stories are meant to show that Jesus fulfilled the prophecy of Micah 5:2, and Matthew himself indicates in clear terms, by quoting the very prophecy.

And so what conclusion can we draw? To me it seems all fairly straightforward. Jesus was not really born in Bethlehem.

OK then, if not there, where? He came from Nazareth. I can’t think of a single good reason to think he wasn’t born there.
- Dr. Bart D. Ehrman

Matthew found his own way of addressing this problem - he claimed that Jesus was born in Bethlehem, because his parents lived there, but the family was forced to flee when Herod tried to kill all the newborn boys in the town; after a period of living in hiding in Egypt, the family relocated to Nazareth.

Luke's solution to the problem of Jesus' birthplace was different: according to Luke, the family lived in Nazareth, but had to go to Bethlehem for the census.

While we might take exception to this apparent disregard for historical accuracy, it wouldn't have been a serious problem for people living in the ancient Roman Empire. Keep in mind that people living around the same time as Jesus, or shortly after his death, would have known perfectly well that neither the slaughter of infants nor the census had taken place in the manner described by Luke and Matthew. They didn't care about the historical inaccuracies, because this kind of writing was commonly understood to be concerned with moral truths, not what we would call "historical accuracy". The moral lesson of a text was independent of its adherence to literal accuracy. The point is more important than the precise details of the narrative.

By way of comparison, the original version of Mark ends with the women going to Jesus' grave, finding his body missing, and being told by an angel that Jesus had been raised from the dead. The last line of the passage says "Being afraid, the women ran away from the place and told no one of what they had seen". The logical problem with this account should be obvious: If the women never told anyone what had happened, how did Mark find out about it?

There are similar issues with Matthew and Luke: In the Garden at Gethsemane, the disciples fall asleep, and Jesus walks away to pray alone. The words of his prayer are recorded in the text, despite the fact that no one was awake to hear them.

This kind of situation is only problematic for us in the modern world, because we have come to value a scientific approach to historical studies. We tend to give precedence to objective accounts of facts, dates, etc, and this is a good thing. But we run into trouble when we expect the ancients to share our views and standards. The ancient Romans lived in a different context than we do today, and it is futile to look for modern values in ancient texts.

Most modern biographies are full of data – names, dates, places, and events – all of which show a concern for factual accuracy. A modern biography, of course, can deal with the whole of a person’s life or with only a portion of it. Typically it is concerned with both public and private life and with how the subject both reacts to what happens and is changed by it. In other words, the inner life of the person, his or her psychological development based on events and experiences, is quite often a central component and is used to explain why the character behaves and reacts in certain ways. Thus modern biographies tend not only to inform but also to explain. They also are meant to entertain, of course, and often propagandize as well, especially when they concern political or religious figures.

Most ancient biographies were less concerned with giving complete factual data about a person’s life, or a chosen period of it. Research methods were necessarily different, with few surviving documents to go on, and (by our standards) inadequate tools for record keeping and data recovery. Biographers often relied heavily on oral information that had circulated for long periods of time. Indeed, many of them expressed a preference for oral sources, for an obvious (to them) reason: such sources could at least be interrogated (as opposed to written texts)! Modern biographers tend to be leery of hearsay.

If I were to attempt a definition of the Greco-Roman biography, then, it might be something like this: ancient biography was a prose narrative recounting an individual’s life, often within a chronological framework, employing numerous subgenres (such as sayings, speeches, anecdotes, and conflict stories) so as to reflect important aspects of his or her character, principally for purposes of instruction (to inform about what kind of person he or she was), exhortation (to urge others to act similarly), or propaganda (to show his or her superiority to rivals).

The Gospels of the NT, as I’ve indicated, are widely today seen as (religious) biographies, and they need to be read as such (for a convincing and full study of the matter, see Richard Burridge, What Are the Gospels? Comparison with Greco-Roman Biography). We should not expect heavily documented data based on extensive archival research. We might expect them to have a miraculous beginning and end. We might look for descriptions of the subjects divinely inspired teachings and supernatural deeds. We should not look to find anything like character development. Instead, we should look to see how the character (Jesus, in this case) acted and reacted to the various challenges with which he was confronted, demonstrating who he was through his carefully crafted words and impressive deeds. And most especially, we should expect to see important aspects of his character and identity at the outset of the narrative, in the opening scenes of the action – since that is where the distinctive features of a biographical subject are established for the careful reader.
- Dr. Bart D. Ehrman

Conclusion:

The simple answer to your question is that censuses didn't work the way Luke seems to think they did.