One thing I notice about the debates on both tax policy and income inequality is that a lot of people seem to have relatively hazy ideas about how income is earned in America, and how much of each kind of income there is. For example, if someone is earning $300,000 a year, where is their income likely to be coming from? How much revenue is drawn from capital gains taxes? And how is income distributed between corporate shareholders and workers? People don't tend to have very strong priors about the answers to these questions, because they simply haven't yet learned what the relative sizes of different sources of income actually are.
Portfolio income can come from multiple sources – interest/bond coupons, stock dividends, financial strategies including derivatives and capital growth. Each offers some cash flow and some also offer potential capital gain with some risk from liquidity and volatile prices. In this low-yield environment, many investors rely too heavily on cash flows and to pursue this are venturing further into riskier areas than they’d normally consider.