Bitcoin tumbles to its lowest level since September 2017

Bitcoin was down 5% Monday and trading at its lowest level in over a year.
It has fallen 40% since November 14, a few days before a hard fork in its rival bitcoin cash.
Watch bitcoin trade live.Bitcoin and its rival cryptocurrencies were under pressure Monday as the relentless sell-off that began less than two weeks ago continued.
Early selling Monday had bitcoin, the largest cryptocurrency by market value, down 5% to near $3,800 and trading at levels last seen in September 2017. Bitcoin has see