HOULTON, Maine — After months of delay thanks to COVID-19, the U.S. Census Bureau will resume sending out door knockers for in-person visits to tally the population.

And one of the first places in the country they’re visiting in Update Enumerate is northern Maine, which the Census Bureau defines as the northern parts of Aroostook, Piscataquis and Somerset counties. It is one of two areas in the United States where they are sending people to take the tally. The other is southeastern Alaska.

The bureau’s Update Enumerate operation sends census takers to the geographically remote, hard to reach areas, where they update addresses and collect responses in person, rather than by mail or online.

The operation officially restarted on June 14, and census workers are expected to begin field work on June 22.

“We’re getting to the more rural areas first to ensure that we’ve got this accurate count,” said Lisa Moore, assistant regional census manager at the New York Regional Census Center, which is the Census Bureau’s office for data collection in the Northeast. She said the lack of reliable data on address locations and number of addresses meant the areas had to be surveyed in person.

The three census tracts for each county that will be visited had a population of 4,389 in the 2010 census, spread over an area larger than Connecticut. Update Enumerate accounts for only 0.01 percent of U.S. households.

But the areas are geographically isolated, and can be difficult to access at certain times of the year — such as during mud season, when roads become muddy due to thawing ground in early spring.

The resumption of census work comes as Maine, like other states, is reporting lower self-response rates — the percentage of households that mail back census forms on their own — than in 2010. Lower self-response rates indicate that more people may be unaccounted for, which can affect how much political representation a state has.

Maine has a self-response rate of 50.8 percent, compared to a 57.4 percent response rate for the 2010 census. In some Maine counties, the response rates are even lower and the disparities from 2010 are even greater.

For example, Aroostook County currently has a self-response rate of 49.5 percent, compared to 55.7 percent in 2010. Hancock County has a rate of 39.1 percent, compared to 47.5 percent a decade ago. And in Piscatquis County, the self-response rate is only 35.8 percent, compared to 44.4 percent in the last census.

The Census Bureau also keeps estimates of which census tracts are likely to have lower self-response rates, in terms of percentage of households likely not to self-respond. Percentages in Maine census tracts range from as low as 10.6 percent to as high as 31.6 percent.

“Our partners throughout the state of Maine have been very influential in combating that predictor,” said Moore. “We use that as an area to focus efforts and resources and partners’ conversations in those areas, because we predicted X percent will not self-respond.”

The most recent data suggests that these rates are improving. Prior to this week, Piscataquis had a self-response rate of only 28.5 percent. But in the last week, the number jumped to its current 35.8 percent.

The jump can be attributed to the recent completion of Census Bureau’s Update Leave program, where census workers physically drop off paper questionnaires to be filled out at addresses that generally do not receive mail.

With Update Enumerate on its way next week, the bureau will look for rates to continue to increase. For the three tracts covered by the operation in Aroostook, Piscataquis and Somerset counties, the response rate currently stands at 38.8, 11.9 and 13.3 percent, respectively. In Piscataquis County, the Update Enumerate area accounts for 15 percent of all households in the county.

“The state partners were very excited because they’ve been working hard to move this response rate, and they’re finally seeing that come to fruition,” says Moore. “They’re very unique and they’re doing some great stuff, so we’re excited about that.”