Less than two months of 2024 have passed, but the year has already been a pleasing one for stockmarket investors. The S&P 500 index of big American companies is up by 5%, having passed 5,000 for the first time ever, driven by a surge in enthusiasm for tech giants, such as Meta and Nvidia. On February 22nd Japan’s Nikkei 225 passed its own record, set in 1989. The roaring start to the year has revived an old debate: should investors go all in on equities?