Fifty-six percent of California farmers were unable hire the amount of employees they needed at some point in the last five years and more than half have started using mechanization, according to a survey released on Tuesday.

"Part of this issue is driven by labor supply factors. The farm labor force in the U.S. is aging, and it's not really being replaced by young immigrant workers the way it once was, " Zachariah Judson Rutledge, a U.S. Davis doctoral student and the lead author on the study, told Newsweek. "One of the main factors was there's an expanding economy in Mexico for both farm work and non-farm."

Rutledge also said that the amount of the farm labor force that would migrate to harvest different crops had decreased, contributing to the worker issues, and that immigration policy had an impact on the number of farm workers seeking to enter the country.

"Immigration policies are playing a role, too. There's some evidence and some studies that it's costing workers higher fees to get smuggled across the border," he said, noting that the cost of entering the country rose, lower numbers of people would seek to enter the U.S. to do farm work.

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