The metro areaâs 2013 population of 6.3 million ranks fifth among U.S. metropolitan statistical areas. The Houston MSA covers 9,444 square miles, an area larger than New Hampshire. ï· The Houston MSAâs nominal gross area product in 2013 was $532.9 billion, according to The Perryman Group. If Houston were a country, its economy would be larger than that of Norway or Venezuela, according to the World Bank.