I saw a couple of comments today about the price of USDT so I think it's worth while explaining how it works just in case anyone is interested in knowing more.
USDT is a pegged-currency. It's often described as a stablecoin but that's not correct because it doesn't have an inbuilt stabilisation mechanism unlike Maker's DAI for instance.
The way it works is purely based on well known legal mechanisms that have no cryptoeconomic properties on its own. The issuer holds a USD balance at a bank, then commissions a receipt that proves their balance and issues an equal number of USDT. 1 USD = 1 USDT at issuance time and the trustworthiness of both the issuer, the auditor and banks involved.
The token itself is used to facilitate trading and many investors 'park' their gains in USDT while waiting for the market to reach a certain point or just in between trades, but that means that the token's FX value is set by the open market itself so if there are more buy orders than available USDT the price goes up and if there are more sell orders than demand the price goes down. Where this gets interesting is that some exchanges list assets based on the USDT fx and not USD which opens some arbitrage opportunities like we are seeing today.
For more info:
https://github.com/jpantunes/awesome-cryptoeconomics#stablec...
https://stablecoinindex.com/