ARRL published an article talking about the number of new hams that came to us in 2017. For the fourth year in a row, more than 30,000 new hams.
At the end of 2017 the US Amateur Radio population stood at 748,136, this is a net growth of 5,349 over 2016.
Please see their article for overall numbers from 2008-2017 and the significant growth in the number of licensed hams.