While the number of rural self-employed workers has gown by 240 percent over the past four decades, their income remains about half of what traditional wage and salary workers earn, according to a report by the Rural Sociological Society, an inter-university research group.

If current trends continue, one in three rural workers will be self-employed by 2015, the report shows.

The report urges policymakers to boost public funding for daycare centers, courier services, accounting services and other businesses that help these small-business owners operate more efficiently. At the same time, local governments should keep better track of self-employed workers in order to more effectively serve them as a growing segment of the labor force.

According to the report, the Midwest relies more heavily on non-farm self-employment than coastal regions. The highest average income for self-employed workers was in New York, where they earned $138, 500. The lowest was in Flagler County, Fla., at $2,600.