NEW YORK — The average 401(k) balance rose a record 17 percent last year to $112,300 from the end of 2018, according to a review of 17.3 million accounts by Fidelity Investments.

The average individual retirement account, or IRA, balance rose the same percentage to $115,400.

Those figures are averages, not medians, and the typical 401(k) might be closer to a quarter of that.

Surging markets around the world were a big reason for growth across accounts in 2019: The S&P 500 index had one of its best years in decades with a 31.5 percent return. Investments of all types logged gains, from junk bonds to stocks from developing economies.

Workers’ savings habits also played a big role.

Fidelity said the average worker set aside 8.9 percent of their pay in their 401(k) in the fourth quarter, a record. Combined with employer matches, the average total savings rate was 13.5 percent in the quarter, tying a record last reached in the spring of 2019.

Such figures also, though, count only people who have a 401(k). Many lower-income workers, particularly at smaller employers, could not save in a 401(k) even if they wanted to because their companies don’t offer access to one.

Nearly half of all U.S. households aged 55 and over, or 48 percent of them, had no retirement savings at all as of 2016, according to estimates from the Government Accountability Office.