Supposedly rich get richer in economy (and life). Those who claim this to be a fact, usually, state that the reason is because the income from labor (wages) grows slower than return on capital. So capitalists accumulate wealth faster than workers.
If you'd like to claim that it's happening on CV, then you'd have to map CV's domain to capital and labor. You say that upvotes are capital (wealth), and labor is answering questions. If that's the case then by simply owning (managing) capital you must be getting upvotes. I don't think that's the case here. You can't simply do nothing and get upvotes on a new question. You have to answer it at the very least.
Your hypothesis is that people with many upvotes get new upvotes faster. However, that's more like getting higher wage based on length of service and prior achievements in real life.
So, I'm not saying that rich are not getting richer here at CV. Yet, I'm saying that if that's the case it's a completely different phenomenon from the economy. The mechanism would be very different.
To answer @amoeba comment. I thought about this too. This scenario is not what OP was talking about. He's not talking about getting upvotes on the questions that you answered long ago, I think. Of course if you have a lot of reputation it means that you answered a lot of questions, and those questions got a lot upvotes. People who come here to ask the same question, will be likely to upvote you. So, it's a different kind of phenomenon still
Let's look at a few top performers in Year 2017. I pulled this data CV, ranked down by number of reputation points this year:
156,068 4,446 whuber 0.028487582
10,009 1,775 mathew gunn 0.177340394
33,083 1,256 amoeba 0.037965118
2,129 690 studentt 0.32409582
907 644 morganball 0.710033076
The guy with least amount of total reputation has the highest return on the reputation, i.e., ratio of reputation points in 2017 vs. total is 0.71. Otherwise, there doesn't seem to be clear pattern here.
Here's the chart with OP's reputation growth. If OP's claim were true, then he should have seen the exponential growth in reputation: while his reputation grows, his upvote collection should accelerate. However, this chart shows linear growth in reputation. My chart looks very similar too.