Tether rose quickly to $9.1 billion in 2020 as supply doubled since March, but some of that is old money being repurposed into USDT.
Source: https://cointelegraph.com/news/sizeable-portion-of-tethers-45b-growth-comes-from-exchange-fiat
Sizeable Portion of Tether’s $4.5B Growth Comes From Exchange Fiat
July 21, 2020
CoinTelegraph