Efforts to shield Americans from surprise medical bills—such as the No Surprises Act—may be starting to work. A recent analysis showed two million surprise bills had been avoided in a two-month span.

Now, a new survey of more than 1,000 US workers with employer-sponsored health insurance shows that consumers are doing their part to push back on incorrect medical bills.

According to data released today from employee benefits company Optavise (formerly DirectPath), approximately one-third (35%) of respondents said they had received an incorrect bill in the past three years and 87% of them had pushed back, asking for a new one , corrected bill.

Some respondents paid the incorrect bill even though they knew it was wrong. Of these, 70% said it was because the amount of the error wasn’t worth the effort to fix it, a substantial jump from 43% in a 2021 version of the survey. The other 30% said it was because they didn’t know how to fix it, another significant change—down from 52% in 2021, suggesting Americans may be getting savvier about their medical bills.

Despite these potential signs of progress, significant gaps in Americans’ healthcare literacy remain.

Though most survey respondents (71%) reported that they understand key health insurance concepts, 10% admitted they didn’t know what an insurance “premium” is (the set monthly fee you pay for insurance coverage) or what an “out-of -pocket limit” is (the cap on what you have to pay on deductibles, copayments, and coinsurance).

Almost as many (8%) said they don’t know what “in-network” and “out-of-network” mean, terms that refer to whether healthcare providers contract with the health insurer (in-network) or not (out -of network).

Other common terms also confused some people. Six percent of respondents said they didn’t know what a “deductible” is (the amount you pay for services before health insurance pays for anything). That was triple the percentage who didn’t know it in 2021. The same portion didn’t know what a “copay” is (the fee you pay each time you healthcare services), double last year’s rate.

For many respondents, health insurance concepts are self-taught; 34% had educated themselves through online or other resources. Just 30% had learned about health insurance from their employer’s human resources team, down from 37% in 2021. One-fifth (21%) had learned from a third-party benefits educator or other resource provided by their employer, up from 16% last year.