What word means "change in wealth over time?"

Over at https://money.stackexchange.com/q/146575/75566 we haven't come up with an English word that unambiguously means "change in wealth over time." My perhaps naïve first shot at this was "income." It turns out that "income" is overloaded and does not communicate what I think it does. For instance, some very wealth people have zero income. What world in English could we use to unambiguously talk about someone's "change in financial wealth over time?" Talking about a person's "yearly income" brings up too much debate about what income is, exactly; so, what word could we use to introduce clarity to the sentence.

While Bill Gates recorded a taxable income of $0 last year, over that same period his __________ was $3.5 billion; that means he paid zero taxes on his $0 income while increasing the financial wealth that he controls from $30 billion to $33.5 billion.

What is the one English word that can fill in the blank?


A possibility is net wealth increase. Examples of usage:

The impact of the net wealth increase on consumption is calculated using marginal MPC by net wealth deciles estimated by Carroll et al.
R. O'Farrelli, Ł. Rawdanowiczi, and K.-I. Inabai, "Monetary Policy and Inequality," OECD Economics Department Working Papers, ECO/WKP(2016)5 (2016). (source)
This is just a result of the fact that, as taxes grow, benefits must also grow to produce an equivalent net wealth increase.
R. Moffitt, "Trends in Social Security Wealth by Cohort," in Economic Transfers in the United States, M. Moon, ed. (University of Chicago Press, Chicago, 1984). (source)
Microsoft Corporation co-founder Bill Gates's estimated net wealth increase makes him the second person after Amazon.com Inc's Jeff Bezos to join the centibillionaire club.
"Meet the World's Two Centibillionaires," Al Bawaba News (March 21st, 2019). (source)
While a gain of one percentile in the income distribution is associated on average with a relative net wealth increase of roughly 0.4 percentiles, quantile regressions show the non-linear behavior of this relation.
S. Humer, M. Moser, and M. Schnetzer, "Inheritances and the Accumulation of Wealth in the Eurozone," ICAE Working Paper Series No. 73 (2017). (source)