Upvote:3
Scholars argue over the very basics of the functioning of the comitia centuriata . Here is the nearest to a hard number I could come up with. The total number of equites in the late Republican/Augustan period is generally thought to be around 10-20,000 (much scholarly squabbling, but most guesses converge around here). The census of 86BC counted 463,000 Roman citizens and the 70BC census (after the Social war expansion) counted 910,000. Since the equites had 18 out of 193 centuries, 1-2% of the electorate had 10% of the vote. But there are lots of other points to consider - only citizens actually in Rome or who came to Rome could vote, we don't know the relative sizes of the tribes, the numbers of juniores compared to seniores, how strong exactly the moral influence of the centuria prerogativa was, etc. In fact, Fergus Millar has challenged the general belief that the poorer Romans were so without electoral and political influence (p.16-17).
Upvote:4
This graph seems to show somewhat of you're looking for:
http://mappinghistory.uoregon.edu/english/EU/EU02-02.html
The graph shows that:
I believe these are the official census numbers, which should be taken with a large grain of salt since counts were done in different ways at different times.
I've been finding this kind of information really hard to come by : /