RALEIGH (WTVD) -- For the third year in a row, Raleigh made the top three cities for the best quality of life in the world according to Numbeo.com. In 2017, Raleigh was second on the list, but before that the City of Oaks had never cracked the top 100. In 2018, Raleigh was also ranked third in the world.For those three years, Numbeo ranked Raleigh as the top American city for quality of life.According to Numbeo.com, the quality of life index is "an estimation of overall quality of life by using an empirical formula which takes into account purchasing power index, pollution index, house price to income ratio, cost of living index, safety index, health care index, traffic commute time index and climate index."Charlotte came in at 10th on the list. Raleigh and Charlotte also rank in the top ten for local purchasing power, which shows "relative purchasing power in buying goods and services in a given city for the average wage in that city."