We've known for a while that Apple has a mind-bogglingly large stockpile of cash: $147 billion, as of the latest count. On Tuesday, we learned that it's also a huge chunk of the total amount of cash held by U.S.-based companies overall, not including banks: About 10 percent, according to a report from Moody's.

The more interesting thing, though, is how Apple's domination reflects an increasingly unequal cash distribution across American corporations generally.

First of all, it's important to note that cash reserves have been rising steadily over the past five years, as corporations seek to shore up their reserves -- a behavior known as "liquidity preservation" -- in an uncertain economic environment. "The financial crisis really highlighted a greater need to get better control of your own financial future," explains Moody's analyst Richard Lane.

Another factor may be the compounding effects of globalization. Companies are making more and more of their profits overseas, and lose a lot of it to the U.S. Treasury when they bring that cash back home, which they have to do in order to paying dividends and doing share buybacks. So they've tended to sit on it instead -- and now, 61 percent of the total stockpile is stored outside the U.S.

But the ballooning reserves haven't been equally distributed. The 50 richest companies accounted for 64 percent of the $1.48 trillion total cash pile as of mid-2013 -- up from 61 percent last year, 59 percent in 2011, and 54 percent in 2006.

What's going on there? Well, it's not just Apple: The top four are rounded out by Google, Microsoft, and Cisco Systems. Lane says rising inequality has a lot to do with the emergence of tech companies that are both extremely profitable and have relatively low staffing costs and capital expenditures (compared to, say, Walmart, which is number one on the Fortune 100 but has only the 28th-largest cash pile). They also tend to pay lower dividends and do fewer buybacks, keeping more of it to themselves.

It's not by any means a perfect analogy to the economic inequality that's been growing in the United States for decades now. But it's interesting to see that corporate America isn't immune.