With a population of over 9 million spread over , Cairo is by far the largest city in Egypt. An additional 9.5 million inhabitants live in close proximity to the city. Cairo, like many other megacities, suffers from high levels of pollution and traffic. The Cairo Metro is one of only two metro systems in Africa (the other being in Algiers, Algeria), and ranks amongst the fifteen busiest in the world, with over 1 billion annual passenger rides. The economy of Cairo was ranked first in the Middle East in 2005, and 43rd globally on ''Foreign Policy'' 2010 Global Cities Index.