NEW YORK - The deep declines in the U.S. stock market over coronavirus fears the last three weeks have left a dent in retirement portfolios and brokerage accounts, costing on average each person in the United States around $16,000 as of Monday’s close before a rebound Tuesday erased some of those losses.

That does not account for wealth disparity and spread of ownership of stock. According to an analysis of 2016 Federal Reserve data by Edward Wolff, an economics professor at New York University, 84% of stocks owned by U.S. households are owned by the wealthiest 10% of Americans.

Here is a breakdown of stock ownership and how much risk ordinary investors face:

The U.S. retirement system no longer relies on defined benefit pension plans - which pay out a guaranteed amount until death. That means that people are mostly in charge of their own retirement, investing via 401(k) plans.

It also means financial pain is personal. When the market fell 7.6% on Monday, the average person became poorer by $5,682, according to calculations by S&P Dow Jones Indices senior index analyst Howard Silverblatt.

Around 42% of the working-age population with a full-time job has a 401(k) or similar plan, and those funds are overwhelmingly invested in stocks, according to U.S. Census data.

According to the Investment Company Institute there are $5.9 trillion in assets in 401(k) plans overall, with $3.8 trillion in mutual funds. According to Morningstar, $1.7 trillion is invested in target-date funds which have a target on when a person retires and are typically heavily weighted to stocks.

Investors - either through their own choosing or through target-date funds or on the suggestions of financial advisers - focus heavily on stocks because they can pay rich rewards. Stocks have returned an average of 10.5% a year since 1970, according to Morningstar.

That is greater than the 8.3% annual return on bonds over the same time according to Morningstar. Bonds, meanwhile, are unlikely to post the same returns in the future because yields, which move lower as prices rise, are at historic lows.

Overall, individual stock ownership in the United States appears to be declining as more members of the outsized Baby Boom generation retire or shift their portfolio to a more conservative stance in preparation for retirement.

Approximately 55% of Americans reported that they owned stock in April 2019, down from the average 62% who reported owning equities in surveys conducted between 2001 and 2008, according to Gallup data.

However, the popularity of exchange-traded funds, which allow investors to bet on a trend or sector, has surged. There was $4.42 trillion in ETFs listed in the United States overall at the end of 2019, according to ETGI. That has grown by an average of 18.8% a year over the last 10 years.