S&P Global Ratings has assigned Tether a low asset quality score, raising concerns about the stability of its reserves. Tether's Bitcoin reserves account for approximately 5.6% of USDT's total circulation, surpassing its 3.9% over-collateralization rate. This reliance on Bitcoin and other high-risk assets could undermine USDT's reserve coverage if their values decline. S&P, alongside Moody's and Fitch, is recognized as one of the top three global credit rating agencies, and it evaluates stablecoins on a scale from 1 to 5, with 1 being the strongest and 5 the weakest.