Carriers might have already enrolled most of the uninsureds who have the money and energy to buy coverage.
Many state-based exchanges said enrollment activity fell between December and January.
This week, analysts have published several survey reports suggesting the drop could reflect an easing of pent-up demand for coverage.
Gallup polled 1,533 adults. The percentage of uninsured adults who said they’re more likely to buy enough coverage to avoid the penalty rather than pay it fell to 55 percent in February, from 63 percent in November.
The Urban Institute, a think tank, polled 7,873 adults in December.
Nineteen percent of the uninsured adults in the Urban Institute sample said they’d tried looking for coverage through a public exchange, and 33 percent said they’d shop through an exchange later.
But 25 percent said they had no interest in using an exchange, and 23 percent said they hadn’t heard about the exchanges at all.
The consultants at McKinsey conducted a series of four consumer surveys, with sample sizes ranging from 1,040 to 2,096.
The percentage of participants in the McKinsey sample who needed coverage and bought it jumped to 58 percent in February, from 19 percent in late November and early December.
The percentage who hadn’t shopped at all dropped to 30 percent, from 49 percent, and the percentage who’d shopped but not enrolled in a plan fell to 22 percent, from 32 percent.
But the picture was different for consumers who needed to replace coverage and consumers who were uninsured in 2013.
About 82 percent of the coverage replacers had selected coverage by February, up from 39 percent in the fall, and the percentage who had shopped for coverage without buying any had fallen to 11 percent, from 29 percent.
Among the uninsured, the percentage who had selected coverage had increased to 10 percent, from 1 percent, but the percentage who had shopped without enrolling in coverage had fallen just slightly, to 34 percent, from 35 percent.
The percentage who hadn’t shopped at all fell to 56 percent, from 64 percent.
PPACA is supposed to provide premium subsidies for people with low incomes, but only one-third of uninsured people who were eligible for subsidies seemed to know much about them, the McKinsey analysts found.