Minerals are fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels—basic (mining), intermediate (processing), and manufacturing. The estimated growth rate for the real GDP of the United States for 2005 was 3.6%. The nominal GDP was about $12.5 trillion. Housing starts were up more than 4% for the year, and the unemployment rate decreased to about 5.1% in 2005 from 5.5% in 2004. The prime interest rate increased from 5.25% at the beginning of the year to 7.25% at the end of the year.