Small businesses remained optimistic in May, but few had plans to hire more workers, according to a poll released Thursday by online payroll services company SurePayroll.

SurePayroll's report found that 50 percent of the surveyed small-business owners are "experiencing increased revenue and growth in their business," but those same business owners also said that "productivity is outpacing the need to hire," the study said.

"Small businesses have made themselves more efficient through technology during this recovery," SurePayroll CEO and president Michael Alter said in a statement. "However, it creates a holding pattern situation for the economy where increased hiring is not yet necessary."

The study, which compiled data from over 35,000 small businesses, found 64 percent of respondents were optimistic. That's well above the low of 33 percent in September of last year. Still, hiring and paychecks showed little change, both down 0.1 percent from April.

SurePayroll's findings mirror research released by entrepreneurship think-tank The Kauffman Foundation in early 2011 that revealed a startling trend: Businesses are starting with fewer workers than historic norms and are also adding fewer workers as they grow.

Adoption of new technologies, Kauffman's report found, increased productivity but led to new businesses keeping payrolls leaner.