What’s also really important to realize here is that when I took the exam I was teaching people to study for, I didn’t get a perfect score. In fact, I didn’t even get close to a perfect score. I passed. But I also knew a lot about this exam—way more than somebody who was just getting started diving into studying for it. And it was because of that, because I was just a few steps ahead of them, that they trusted me to help them with that information. To support this, I provided a lot of great free value to help them along the way. I engaged in conversations and interacted in comments sections and on forums. Most of all, I just really cared about those people, because I struggled big-time with that exam myself.
The source of pension payments is determined by the portion of the distribution that constitutes the compensation element (employer contributions) and the portion that constitutes the earnings element (the investment income). The compensation element is sourced the same as compensation from the performance of personal services. The portion attributable to services performed in the United States is U.S. source income, and the portion attributable to services performed outside the United States is foreign source income.
Case Schiller only tracks price appreciation of RE. RE as rental investment vehicle is measured primarily on rental yield or cap rate or some other measure. Price appreciation in that scenario is only a secondary means of growth, and arguably should be ignored as a predictor of returns when deciding on whether or not to invest in rentals. More important key performance indicators for rentals are net operating income and cash ROI. Appreciation, if it occurs, is a bonus.
Now, all that said, if capital (savings) grows faster than the growth of the economy, those with savings will see their wealth grow at a faster rate than those who rely on the growth of their income. While this is not an extension of Piketty's argument (you can't take an idea that applies to a population and a whole economy and boil it down to the individual like this), it's not an unreasonable conclusion to take and apply to your own life. (Piketty does talk about this on an individual level, but says it's more impactful for billionaires vs. millionaires – though we have limited data into individuals)
For a person working for a wage, their source of income is their job, or their labor (aka their time that they sell to someone). But you can own a house, and rent it out, and when your renters pay you renter every month, the source of that income check is your rental property, or your house. It would just be called rental income. If you have money in the bank in an account that pays interest, those interest payments are another source of income. We can say the source is interest payments, or we can identify the asset that is generating rent, and say your money in the bank that is generating “rent” (aka interest) is your source of income.