The United States has the largest economy in the world, though it saw slowed growth after events like 9/11 and the recession in 2009. However, the economy has since strengthened due to increased business and consumer spending and lower unemployment. Politically, the U.S. has the oldest democracy with a federal system and three branches of government. It also has a progressive tax system and strong labor laws. Socio-culturally, an aging population and illegal immigration are concerns, though education and healthcare are highly developed. Technologically, the U.S. leads in research and development spending and innovation.