Worldwide HR service spending will experience a compound annual growth rate (CAGR) of 9.6% through 2009 to reach $113.4 bln, as compared to $71.9 bln in 2004. HR business process outsourcing (BPO) is the fastest-growing segment of HR services and predicts that it will grow at a CAGR of 16.1% to reach over $16 bln in the US by 2009.