It's defined relative to the total supply, i.e. total currency in circulation. The supply is controlled by a government body called the Federal reserve.
@APompliano @bquittem @dergigi @hodlonaut @melikmanukyan @saifedean @ProofOfSteve @Rhythmtrader @cryptoquotation
@danheld @100trillionUSD @AleksSvetski @CitizenBitcoin @SimonDixonTwitt @thibm_ @real_vijay
Please correct me if I got something wrong.