I'm not sure that the reason tether is moving is because of the market. I think Tether is moving right now because of rumors of problems with the funding behind the currency. More on that in my post here: https://steemit.com/tether/@amdazed/thoughts-and-discussion-using-on-usdt-tether-crypto-currency-rumors-and-the-potential-to-crash-bitcoin-btc
RE: If you want to know whether the market is moving up or down, just look at Tether. If Tether is up the market is down and if Tether is down the market is up. People moving in and out of USD.