This renewed growth rested on shaky foundations. Mexico's external indebtedness mounted, and the peso became increasingly overvalued, hurting non-oil exports in the late 1970s and forcing a second peso devaluation in 1980. Production of basic food crops stagnated and the population increase was skyrocketing, forcing Mexico in the early 1980s to become a net importer of foodstuffs. The portion of import categories subject to controls rose from 20 percent of the total in 1977 to 24 percent in 1979. The government raised tariffs concurrently to shield domestic producers from foreign competition, further hampering the modernization and competitiveness of Mexican industry.