The Pareto principle says that for many outcomes, roughly 80 percent of the effects come from 20 percent of the causes. Italian economist Vilfredo Pareto noticed in 1906 that about 80 percent of the land in Italy was owned by 20 percent of the population, and the pattern became known as the 80:20 rule. Decades later, management consultant Joseph Juran used the idea in quality control, arguing that most defects usually come from a small number of causes and that fixing those brings the largest gains. The rule is mathematically linked to power law distributions, which appear in many natural and social systems, such as city sizes and word frequencies. Businesses often use it in the form that 80 percent of sales come from 20 percent of clients. The numbers are a rough guide rather than an exact law, and the exact split varies from case to case.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.