The institute says the hole in the protective layer of stratospheric ozone decreased in size to about 8.5 million square miles, compared to 9.25 million square miles last year.
The ozone hole forms during the end of the southern winter in August and September of each year, then breaks up in November or December, according to the institute.
“We have now had a few years in succession with less-severe holes. That is an indication we may be beginning to see a recovery,” institute scientist Stephen Wood said in a statement.
Recent studies point to a nearly complete recovery of the ozone hole by the middle of this century, thanks to an international agreement to phase out the use of ozone-depleting chemicals, such as Freon in refrigerators and aerosol cans.