What is the significance of one-third in Revelation?

1/3 is not the whole, not the greater, but the lesser, and shows that God in His mercy does not destroy the greater, but the lesser, desiring to bring all to repentance. And, throughout the entire Bible, the number three references unity, therefore when 1/3 is referenced, unity is broken.

It must first be noted that the Revelation is divided into 3 parts;

Revelation 1:19 KJV

Write the things which thou hast seen, and the things which are, and the things which shall be hereafter;

The first part is the things which the Lord Jesus had already shown him, the second is the things that were and the third part is the things which will be.

where the one third part comes in has mainly to do with the things that were, which in the main cover the Angelic rebellion in Heaven and the ejection of Satan and the rebellious Angels from Heaven.

The Scripture tells us that a third part of the Angels in Heaven revolted with Lucifer.

Rev 12:3 and 4 KJV

3 And there appeared another wonder in heaven; and behold a great red dragon, having seven heads and ten horns, and seven crowns upon his heads.

4 And his tail drew the third part of the stars of heaven, and did cast them to the earth: and the dragon stood before the woman which was ready to be delivered, for to devour her child as soon as it was born.

Ellis Skolfield takes a historicist position, but interprets some of these numbers not as fractions, but as sequences. Thus "a third" does not always mean 33.3% of a thing, it just means the third in a series.

Also, he interprets things like grass, trees, and the like as symbols. Thus trees refers to churches and green grass to sound teaching. One quote from his study guide:

the third part of trees was burnt up, and all green grass was burnt up.” (Shortly after the Cross, the church in the Middle East falls into false doctrine).

See his free download page here: http://ellisskolfield.com/index.php/skolfield-bible-prophecy-study

The significance of one-third in the book of the Revelation is that certain plagues / judgments start with the warning that one-quarter (of this, that and the other) will be destroyed / taken down, then further on, that is upped to one-third, and by the final 7 plagues, everyone on the earth with the mark of the beast is afflicted. There is a numeric progression: from one-quarter, to one-third, to all.

This means that your second question, "Why is everything 1/3 in Revelation?" is incorrect. NOT everything is one-third. The proportions affected start with one-quarter. When the plagues are ratcheted up, that becomes one-third. Then just before the last trump, it's everyone and everything still under Satan's invisible sway.

Start with Revelation 6:7. You already have the verses mentioning one-third, then read Rev. 13:8 & 16 and 16:2-4.

The significance of one-quarter is mentioned in this book, after dealing with the riders on the red horse, the black horse, and the pale horse-rider called Death, with Hell (Hades) closely behind. They are given authority to kill one-quarter of the people on earth, Rev. 6:3-8:

"The Lamb opens the seal, and these canter forward into time on their grisly errand over all the earth, with power given to them from Almighty God to kill the fourth part thereof, again and again, generation by generation. Death effects this and by four means, for the earth, the whole earth, is that from which the fourth part is reaped by the grim reaper, the meanwhile Hell drawing the souls into its habitations until the resurrection at the Last Day... By these things a fourth part of the earth is taken by the direction of the rider on the pale horse, with Hell embracing the souls of the lifeless corpses. The cause is from above; only the means is from below. But fallen man sees nothing but the means... It is a fourth part out of the population, and three quarters of today's people barely notice their passing. Barely notice. Nor yet at all do they hear the hoof-beats of the pale horse at their own heels." (The Revelation of Jesus Christ pp 161-3, John Metcalfe)

Once the significance of a quarter is seen, then when that is upped to a third, it means even more dreadful results from more plagues from heaven are felt on earth. Yet when the plagues are ratcheted up, the only result is that those afflicted by them refuse to repent of their sins! Indeed, they curse God all the more-so! And then they wonder why the final plagues result in everyone being destroyed? Read Rev. 9:18-21 for the reaction of the one-third, then 16:9-11 & 21 for everyone's reaction just at the end. That's the significance. God's judgments make the right-hearted repent and turn to him, but impenitent sinners just curse God even more than before when they experience his judgments! This means God is utterly justified for finally crushing all such ones along with Satan and his hordes - Rev. 19:11-21.

As with any part of Revelation there are primarily four main theories. Coincidentally most of them take the 1/3 literally regardless of the view as represented a significant judgment but minority (only 1/3) implicated result on the things in this world that otherwise sustain life. Here are the main views very briefly and overly simplified as pertaining one example:

The first angel sounded his trumpet, and there came hail and fire mixed with blood, and it was hurled down on the earth. A third of the earth was burned up, a third of the trees were burned up, and all the green grass was burned up. (NIV Revelation 8:7)

Historicist

When barbarians attacked Rome in ~AD 410, there was burning or destroying everything in their path. Approximately 1/3 of the Roman Empire was ravaged.

Preterist

Similar to historicist but everything sandwiched around the sacking of Israel by Rome. Therefore destruction of actual vegetation in the land around Jerusalem. Let's assume around 1/3.

Futurist

The most literal of all views with everything in the future, probably a literal 1/3 of the earth destroyed by nuclear bombs or something like it in whatever kind of bombs that might exists in the unknown future.

Symbolic/Spiritual

Basically the obvious symbolism that can be imagined. For example 'whatever' kind of destruction which at any time damages the earth such as what we see on the news. Maybe 1/3 is actually greater then what is actual but symbolism does not need to literally match the figure employed.

Note: I am a rare bird these days as I have unexpectedly switched from Symbolic to the Historicist view, which is really not that popular anymore. I started out in my teens as a futurist, moved to Symbolic, almost became a Preterist just before resting in my current view, Historicist. This is how I have became familiar with them over the last 25 years.