Complex sentence: Lynchings were frequent as whites used violence to impose white supremacy; rates were high at times of economic stress and, annually, when it was time to settle accounts for sharecropping.
Split into simpler sentences: Lynchings were frequent in this region as whites used violence to impose white supremacy. Rates of lynching were high at times of economic stress and, annually, when it was time to settle accounts for sharecropping.