The leaky sieve of capital gains taxation

The thing to understand about capital gains and taxes is that most capital gains have not been taxed yet, and may never be taxed, unless the tax code is changed. Consider the case of mutual funds:

From 1997-2012 households had a total of $1.75 trillion in taxable net capital gains on mutual fund assets — meaning that this the amount of income they would be taxed on if they realized the capital gains during this period. But how much of this was actually taxed? It turns out, almost none. The total amount of net gains reported on tax returns was $-100 billion, for an overall negative tax rate.

The explanation is, of course, that capital gains are taxed only on realization. And for most mutual fund holders it never made sense to realize their gains, but instead to only realize their losses, a process known as tax loss harvesting.

This is a particularly extreme example of the general principle that the capital gains tax is a particularly leaky sieve, and it is unclear the extent to which the massive capital gains we’ve seen over the past forty years will ever show up on tax returns.

To look over longer time periods, we can use my estimates of aggregate capital gains, compiled from the Financial Accounts, to capital gains reported on tax returns, estimated from the Treasury. The data is below, and again shows that most capital gains have not yet showed up on tax returns:

From 1954-2020 aggregate taxable capital gains in the Financial Accounts totaled $70 trillion. The total reported on tax returns over the same period was $22 trillion, significantly less than a third of the total.

The low levels of taxes paid on capital gains compared with the massive aggregates means that the effective average tax rates on capital gains are vanishingly small.

Will they ever show up on tax returns?

There are a number of reasons why capital gains haven’t shown up yet on tax returns, and research remains to be done on the relative importance of the different causes.

  1. Many wealth taxpayers can avoid realizing capital gains indefinitely by borrowing against their assets rather than selling them.
  2. Unrealized capital gains at death are forgiven entirely, a massive loop-hole known as step-up basis at death.
  3. In a growing economy (or, similarly, in an economy where capital gains are growing rapidly), if only a small percentage of capital gains are realized each year, then even in a steady state the amount realized relative to the aggregate amount will be low.
  4. There are a variety of other loopholes, legal and otherwise, that have allowed wealthy Americans to avoid paying capital gains taxes.

Aggregate capital gains in 2021

I’ve been harping on the importance of capital gains for years — mainly emphasizing that (i) this is a massive and growing source of income, especially for the very wealthy, and (ii) this income is largely untaxed, due to a variety of loopholes around capital gains taxation (iii) the gains are not well understood from a macroeconomic standpoint.

The latest data release from the Federal Reserve contains data through the end of 2021, and it’s a doozie. The top-line number is absolutely huge: $16.2 trillion in nominal capital gains (93.8% of net national income), or $6.97 trillion in real capital gains (39.2% of net national income).

Nominal capital gains
Real capital gains

Most of the capital gains came from equities (very unequally distributed) and real estate (somewhat unequally distributed).

Capital gains were by far the main contributor in the increase in household net worth over the past year. Nominal net worth increased by $18.9 trillion in 2021. Of the total, $2.3 trillion came from savings / increased capital investment, and $16.7 trillion came from capital gains.

Private savings, as traditionally measured in the National Income and Product Accounts, does not include the value of real capital gains. The figure below adds in real capital gains to savings and compares the two magnitudes.