That's odd, because lot of these questions are actually pretty easy to answer. The IRS is good about publishing the data. Given that – and given the recent interest in personal income inequality, I decided to write a little bit about the different kinds of income people report on their tax returns. A longer paper – Sources of Personal Income – is here, but for a brief overview, you might want to check out the top ten sources of income:

Most of us think of investment income as just the cash flow we get from bank interest, bonds, share dividends and property rents, some of which comes via a super pension.  But a more complete view is to also consider how growing the value of your investments can add to your spending potential.  This total return approach generates income from both income and growth to optimise spending from your portfolio across all market cycles, aligning cheap and expensive investments to your goals.