Vacancies show a hot labor market. But they could overstate how hot.

For most of the past year there have been roughly two open jobs for each person looking for work in the United States. So as the Federal Reserve tries to cool the economy and get price increases under control, one measure central bankers are watching closely is how many open jobs are out there. "Vacancies are still almost at a 2- to-1 ratio to unemployed people,"…