Interest in traveling to the U.S. has dropped 17% since Trump's inauguration, according to Hopper, an app for tracking flight price quotes. Hopper tracks between ten billion and fifteen billion airfare price searches every day.

Expand chart Data: Hopper Research; Methodology: Comparing the weekly average flight searches to the U.S. on Hopper during Dec. 29, 2016 - Jan. 18, 2017 and Jan. 26 - Feb. 1, 2017; Chart: Andrew Witherspoon / Axios

Why this matters: International tourism to the U.S. is calculated as an export, so this could increase our trade deficit, which will irk Trump, according to Quartz. Right now, San Francisco, Baltimore, Las Vegas, and Los Angeles airports are the most affected. This is also an indication that there may be fewer tourists visiting restaurants, museums, and landmarks.

A notable exception: Travel interest from Russia is way up at 88%.

It's not normal: There was only a 1.8% decline in interest this time last year, meaning the dip in interest now is not seasonal.

It's not just the travel ban: Interest was already declining in the three weeks building up to the inauguration, and data from 94 of 122 countries indicates a diminished interest in traveling to the U.S.