A growing number of companies are finding it difficult to recruit skilled workers, which threatens to curtail profits and growth, according to a quarterly survey conducted by the Washington-based National Association for Business Economics.

The results reinforce data coming out of the U.S. this year, which show a tightening labor market amid low interest rates and an economic expansion. Many economists expect the jobs market to start putting pressure on wages and inflation, though that phenomenon has yet to fully materialize.

The results of NABE’s July Business Conditions Survey published on Monday showed that 34 percent of respondents have had trouble hiring skilled employees over the last three months, up from 27 percent in January. The Washington-based association polled 101 panelists, who are economists from companies and industry associations.

NABE survey analyst Patrick Jankowski said businesses in Houston, where he’s based, are under pressure to find workers with more than a