Social mobility is the ability of a person to rise in socio-economic status. For example, in the European Middle Ages, social mobility was virtually non-existent as people lived and died in the classes to which they were born; a peasant had no hope of ever becoming a knight or a lord. In the modern, industrialized world, social mobility remains rare but it is still a possibility. The United States is full of rags-to-riches stories. Although these stories are isolated incidents which in no way represent a common scenario, these stories do give hope and inspiration to the poor.