Markets now expect interest rates to increase four times in 2022 as the Fed fights inflation that has lifted growth in the consumer-price index to 7%, a level barely imaginable a year ago. After reaching a vertiginous high of nearly 40 times earnings at the turn of the year, the S&P 500 index of stocks has fallen by 9% in January (markets in Europe and Asia have fallen too, though by less). Markets’ intraday volatility has been just as striking, reflecting investors’ struggle to digest the consequences of tighter money. High indebtedness makes the world economy more sensitive to changes in monetary policy. Central banks must raise rates enough to quell inflation but not so much that they tip economies into recession as interest burdens rise. . . .