The figures tracking the number of foreign visitors are key to the tourism industry making decisions about marketing and employment. Travel and tourism gave the U.S. an $83.9 billion trade surplus in 2016, according to the Bureau of Economic Analysis.

The tourism office focuses on travelers staying at least one night on visas or from visa-waiver countries such as most of Europe who fill out an I-94 form upon arrival. Visa holders could be visiting for either business or pleasure, as treaty traders or investors, or as students or their families. But the tourism figures don’t include legal permanent residents of the U.S.

Even accounting for different definitions and time frames, the numbers haven’t matched up. CBP reported in February that 124.2 million people arrived at airports in the last fiscal year, marking a 4% rise in non-citizens. Arrivals have grown each of the last eight years, according to CBP.

But the tourism office has charted a decline in overseas visitors during a similar time frame. The number of non-resident arrivals to the U.S. dropped 2.4% during 2016 and another 3.8% last year through September, according to the latest figures available from the tourism office.

Adam Sacks, president of Tourism Economics, a Pennsylvania company that analyzes the federal numbers for industry clients, has been studying the discrepancies for months. International travel to the U.S. increased 2% last year, based on data from five sources other than the tourism office: CBP, the Advanced Passenger Information System created by CBP and three private organizations that track data from where travelers begin their trips, he said.

“What that implies is that the data that has been published by NTTO has been significantly undercounted,” Sacks told USA TODAY. “The reason for that is no fault of NTTO. It’s based on the flawed data records received from CBP.”

McAleenan said CBP had noticed the difference in the results, and will work with the Commerce Department to resolve questions about the data.

“There are different ways to slice and dice the data,” McAleenan said. “We’re going to be working to align our data with Commerce for the next year’s report