At the time of the Industrial Revolution, an incredible rise in prosperity that had never before been seen occurred. Only in the western world has a sustained rise in wealth ever developed. Many reasons have been given to explain why this happened, but only one is the key ingredient. Failing to explain the sudden rise in prosperity, the traditional reasons are natural resources, private property rights, imperialism, and less discriminatory laws. Many countries, which have vast quantities of natural resources are very poor while some countries void of resources are very rich, so natural resources is not the answer. Private property also cannot be the one crucial factor because it had been heavily protected in England for centuries prior to the amazing gain in wealth. Imperialism did not greatly enrich the masses because one cannot become rich by stealing from a poor country. Similarly to the protection of private property, England and the Netherlands had been very non-discriminating in their laws. The one key ingredient was the middle class. The nobles had looked down upon them while the poor had envied them, but this changed during the Industrial Revolution. The middle class operated factories, oversaw production, and owned expansive enterprises. Because of this change in view of the middle class, the west oversaw the greatest rise in prosperity in history.