What does doubled mean?
https://www.msn.com/en-us/news/us/the-number-of-us-adults-carrying-a-loaded-handgun-every-day-doubled-to-an-estimated-6-million-in-just-4-years/ar-AA14stzO?ocid=msedgdhp&pc=U531&cvid=07584ac419b24553bd1d35ddbca07cdb
US adults carrying loaded handguns on a daily basis nearly doubled from 2015 to 2019, a new study found.