If it is a liquid asset, you should count unrealized gains as income. If you invested $100k in VOO last year, and it is worth $120k today, then you have definitely made $20k in the last year. That's $20k that you can choose withdraw and spend, at any time. Just because you choose to reinvest the $20k (ie, by letting it ride) doesn't change the fact that you've made $20k. It's really the same as collecting $20k in dividends and then enrolling in the dividend-reinvestment program.