Contribution amounts from workers and employers — though still fairly constant — took a slight hit in the last year.

Among workers with employee-only coverage and an employer contribution, the percentage reporting that their employers contributed $1,000 or more slipped from 28% to 23% in 2013. Similarly, on average, workers with employee-only coverage dropped their HSA contribution levels last year.

But health savings holders with family coverage kept contribution levels relatively steady. While both lower- and higher-income individuals lowered their contributions in 2013, lower-income individuals were less likely to contribute than higher-income individuals. Employer contribution levels among workers with family coverage were mostly unchanged, too.

According to EBRI's report, 11.8 million adults' ages 21–64 (9.7% of the population) were enrolled in a plan with an HRA or HSA in 2013.

An additional 9.3 million reported they were covered by an HSA-eligible plan but had not yet opened the account, meaning that about 21 million adults ages 21-64 with private insurance were either already in a CDHP or covered by an HSA-eligible plan. When their children were included, 26.1 million individuals with private insurance, representing 15% of the market, were either in a CDHP or an HSA-eligible plan, EBRI reported.

Last week, investment consulting firm Devenir reported that HSAs grew to an estimated $19.3 billion in assets and 10.7 million accounts at year-end 2013 and have grown to more than $20 billion in assets during January.