Digital currency bitcoin kicked off the new year by jumping above $1,000 for the first time in three years late on Sunday, having outperformed all central-bank-issued currencies with a 125 percent climb in 2016. Bitcoin - a web-based "cryptocurrency" that has no central authority, relying instead on thousands of computers across the world that validate transactions and add new bitcoins to the system - jumped 2.5 percent to $1,022 on the Europe-based Bitstamp exchange, its highest since December 2013. Though the digital currency has historically been highly volatile - a tenfold increase in its value in two months in late 2013 took it to above $1,100, before a hack on the Tokyo-based Mt. Gox exchange saw it plunge to under $400 in the following weeks - it has in the past two years been more stable.…