Which of the following factors contributed to the economic decline of the 1970s? Responses Development by U.S. companies in the Sun Belt began to export products across the border to Mexico. Development by U.S. companies in the Sun Belt began to export products across the border to Mexico. Increased regulation of prison labor, which created an increase in the cost of labor overall, leading to higher unemployment rates throughout the southern and western U.S. Increased regulation of prison labor, which created an increase in the cost of labor overall, leading to higher unemployment rates throughout the southern and western U.S. Unemployment in the Rust Belt and development in Asia and Western Europe created competition for American businesses. Unemployment in the Rust Belt and development in Asia and Western Europe created competition for American businesses. Labor shortages led to a decrease in domestic oil production, which led to more imported fuel and a dramatic rise in gas prices