LONDON: A strong start for world equities in 2021 after the fastest bear-to-bull market switch last year has prompted market mavens to flag worries about pricey assets, with BofA calling it the "mother-of-all asset bubbles". The torrent of cash sloshing around world markets due to the unprecedented stimulus measures in place to fuel economies coming out of the pandemic-led recession has fed into the euphoric rush to equities, particularly Big Tech. The US Federal Reserve for instance has been purchasing bonds at a record pace, doubling its balance sheet to nearly $8 trillion in less than a year. During the same period, the five biggest tech stocks have seen their market value double.