A strong labor market is proving both a blessing and a curse for Corporate America.

More people at work means more spending on things like apartments or waste disposal, and companies have welcomed that on recent earnings calls. But a shrinking pool of employees means the providers of those goods and services have to pay ever-higher wages, or cope with staff shortages and increased turnover, as they struggle to meet the rising demand.

That's one of the drawbacks of a jobs boom that keeps surprising analysts. The United States added 304,000 workers to payrolls in January—easily topping forecasts, even amid a partial shutdown of the federal government and with unemployment already close to a five-decade low.