New York, Dec 14 (IANS): Doing a PhD may require you to invest a few extra years in education, but the degree can help you earn higher-than-average salaries, new research suggests.

Recipients of PhD degrees in the US earn high wages after graduation, participate in national and international labour markets, and make an important impact on local economic development, the findings show.

Almost 40 percent of these PhD graduates enter industry, where they are disproportionately hired at large and high-wage establishments in technology and professional service industries.

"It (the study) is an important first step in providing policymakers the tools they need to assess the broader effects of investments in science," said one of the lead researchers Paula Stephan from Georgia State University in the US.

With the help of US Census Bureau data, the researchers examined employment and earnings outcomes of nearly 3,200 PhD graduates from eight major research universities.

The study showed more than 20 percent of these doctoral recipients remain in the state where they trained, about 13 percent within 50 miles of their university.

Only a small percentage of the PhD recipients entered government (4.1 percent) and the majority remained in academia (57.1 percent), many presumably taking a postdoctoral research position.

Seventeen percent of the PhD recipients worked in establishments owned by firms with research and development operations versus 10.8 percent of the US workforce.

The researchers also found the median US establishment employing these PhD recipients has a higher payroll per worker -- more than $ 90,000 -- than the median US establishment owned by a research and development firm (just under $ 61,000) and the median US establishment (just over $33,000).

Fifty-one percent of these doctoral recipients work in establishments where per-worker payrolls exceed $100,000, the findings showed.

The study was published in the journal Science.