American workers are leaving money on the table — employer matching funds for their 401(k)s — because they’re just not saving enough to take advantage of the full match.

In fact, according to a report from Financial Engines titled “Missing Out: How Much Employer 401(k) Matching Contributions do Employees Leave on the Table?” says workers are leaving as much as $24 billion every year in employee matching funds they weren’t eligible to receive.

The study looked at how much money 4.4 million retirement plan participants saved at 553 companies, and the results were downright depressing. One out of every four didn’t get the full employer match because they didn’t save enough. They fell so far short that the typical employee missed out on $1,336 every year — equivalent to an extra 2.4 percent of income they didn’t get. With compounding, said the study, this could amount to as much as $42,855 over 20 years.

So who’s missing out, and why? The report found, as might be expected, that younger and lower-income employees were the most likely not to set aside enough for a full match.

Among employees earning less than $40,000 a year, 42 percent couldn’t hit the savings rate that would have brought the full amount of matching funds along with it. Only 10 percent of employees making more than $100,000 per year failed to get the full match.

Employees under the age of 30 were about twice as likely to fail to qualify for the whole amount as employees over 60, too — 30 percent compared with 16 percent.

Those between the ages of 35 and 45, however, tend to hit a rough patch when they too fail to contribute enough to get the full employer match. That could be thanks to family needs or other reasons; the study did not explore the causes for the decline in saving.