Following a period of robust expansion since 2001, economic growth in the United States slowed at the end of 2007. The diffusion of information and communication technologies (ICTs) continues to fuel productivity growth, especially in the business services sector. The United States is an innovation powerhouse, but its lead is increasingly challenged from some of its main international trading partners and emerging economies. R&D intensity fell slightly to 2.6% of GDP in 2006, down from 2.7% of GDP in 2001, although total R&D expenditure expanded in real terms to USD 344 billion, led by increases in business sector R&D spending (USD 208 billion in 2006). The share of R&D performed by government has fallen (to 11.1% in 2006), while that of the higher education sector has grown (to 14.3% in 2006 compared to 12.1% in 2001).