WASHINGTON — Americans enjoyed a healthy increase in income last month but didn’t spend much of the gain.

The Commerce Department said Friday that personal income rose 0.4% in May, up from a 0.3% in April. But consumer spending rose just 0.1% last month after climbing 0.4% in both March and April.

After-tax income rose 0.6%, the biggest gain since December 2012. The gap between the May increase in income and the increase in spending drove the U.S. savings rate to 5.5%, the highest since last September.

Economists monitor consumer spending closely because it accounts for…