Spencer's Principles of Biology was the first to use the phrase survival of the fittest in print. Darwin agreed that the phrase survival of the fittest was better than natural selection . Natural selection personified nature, but was really about survival. Survival of the fittest would avoid this problem, but it "lost the analogy between nature's selection and the fanciers" (breeders). The phrase was first used by Darwin in the 5th edition of The Origin published in 1869,  in which Chapter 4 describes "Natural Selection, or the Survival of the Fittest". 
We study the impact of the minimum wage on firm exit in the restaurant industry, exploiting recent changes in the minimum wage at the city level. The evidence suggests that higher minimum wages increase overall exit rates for restaurants. However, lower quality restaurants, which are already closer to the margin of exit, are disproportionately impacted by increases to the minimum wage. Our point estimates suggest that a one dollar increase in the minimum wage leads to a 14 percent increase in the likelihood of exit for a -star restaurant (which is the median rating), but has no discernible impact for a 5-star restaurant (on a 1 to 5 star scale).