Hundreds of billions of dollars have been wiped off the value of technology companies in recent days, after a major share sell-off. The electric carmaker Tesla was among the worst-hit companies, sliding 21 percent in trading on Tuesday. Investors are concerned that these firms' shares rose too quickly during the pandemic and are now overvalued. Despite the rout, most tech shares are still trading at much higher values than they were at the beginning of the year. Also today, we look at Uber's pledge to use more electric vehicles.