Asset prices are high across the board. Is it time to worry?

IN HIS classic, “The Intelligent Investor”, first published in 1949, Benjamin Graham, a Wall Street sage, distilled what he called his secret of sound investment into three words: “margin of safety”. The price paid for a stock or a bond should allow for human error, bad luck or, indeed, many things going wrong at once. In a troubled world of trade tiffs and nuclear braggadocio, such advice should be especially worth heeding. Yet rarely have so many asset classes—from stocks to bonds to property to bitcoins—exhibited such a sense of invulnerability.