WASHINGTON (AP) — U.S. companies closed out 2017 with strong hiring in December, adding the most jobs in nine months.

Payroll processor ADP says that businesses added 250,000 jobs last month, up from 185,000 in November. The gains were led by robust hiring in health care, professional services such as accounting and engineering, and retail.

The figures suggest that businesses are optimistic about the economic outlook and are staffing up to meet greater demand. ADP's data bodes well for the government's monthly jobs report, to be released Friday. Economists forecast that will show a gain of 189,000 jobs, according to a survey by data provider FactSet.

The unemployment rate is projected to remain at a 17-year low of 4.1 percent.

The ADP numbers cover business payrolls and don't include government employment. They often diverge from the official figures.

The U.S. economy is growing at a steady clip, bolstered by a solid holiday shopping season. Most economists expect the Trump administration's tax cuts to accelerate growth in 2018 by roughly one-third a percentage point.

That should bring down the unemployment rate to as low as 3.5 percent by the end of 2018, economists predict, which would be the lowest in nearly a half-century.

Mark Zandi, chief economist at Moody's Analytics, which helps compile the ADP data, said that healthy consumer spending over the holidays helped lift hiring.

A category that includes retailers and shipping companies added 45,000 jobs, the most since last December. Online shopping has spurred shipping companies such as UPS to ramp up hiring over the holidays.

Consumers likely spent more because they anticipate some income gains from the tax cuts, Zandi said. Strong gains in the stock market in December also likely helped.

"My sense is the tax cuts probably have their fingerprints on the employment numbers," Zandi said.