The area's many colleges and universities make Boston an international center of higher education and medicine, and the city is considered to be a world leader in innovation. Boston's economic base also includes finance, professional and business services, biotechnology, information technology, and government activities. Households in the city claim the highest average rate of philanthropy in the United States; businesses and institutions rank amongst the top in the country for environmental sustainability and investment. The city has one of the highest costs of living in the United States, though it remains high on world livability rankings.