The number of insurers in the HSA survey sample dropped to 64, from a recent high of 95 in 2012.

The reasons are not clear, but America’s Health Insurance Plans (AHIP) received fewer insurer responses for its 2015 health-deductible health plan (HDHP) survey than it received for its 2014 HDHP survey.

AHIP, a trade group for health insurers, says it emailed survey forms to 109 member and non-member insurers this year, down from 113 in 2014.

The number of insurers that responded to the survey dropped 7.5 percent — to 64, from 80.

The number of insurers that received the survey form before 2014 was not immediately available, but the number of HDHP survey respondents is down from a peak of 95 in 2012.

See also: AHIP: Enrollment in HSA-Compatible Plans Jumps

The number of HDHP survey respondents is the lowest number AHIP has recorded in the past six years.

The drop could reflect methodological problems, such as the difficulty of getting emails through more aggressive spam filters, or the effects of Patient Protection and Affordable Care Act (PPACA) demands on insurers’ ability to find time to fill out survey questionnaires.

See also: Watchdog: 30% of health insurers filed PPACA fee forms late and What happened to health broker comp?

The drop could also reflect shifts in insurer participation in the HDHP market.

The respondents reported providing HDHP plans that qualify for the health savings account (HSA) program for 20 million people this year. That was up 13 percent from the 2014 total.

AHIP found that enrollment in the respondents’ individual HSA-qualified HDHPs increased 3.6 percent, to 2 million, and that enrollment in the respondents’ large-group HSA-qualified HDHPs increased 20 percent, to 15 million. Enrollment in the respondents’ small-group HDHPs fell 8 percent, to 2.3 million.

The percentage of respondents with small HSA-qualified HDHP operations fell sharply.

Only 17 percent of the 2015 survey respondents reported having 10,000 or fewer HSA-qualified HDHP enrollees, down from 25 percent in 2014, and down from close to 30 percent from 2011 through 2013.