It's actually 97%, at least as of 2010: http://www.ussc.gov/Data_and_Statistics/Annual_Reports_and_Sourcebooks/2010/FigureC.pdf http://www.ussc.gov/Data_and_St

It's actually 97%, at least as of 2010: http://www.ussc.gov/Data_and_Statistics/Annual_Reports_and_Sourcebooks/2010/FigureC.pdf http://www.ussc.gov/Data_and_Statistics/Annual_Reports_and_S... Unfortunately that's down at the moment but you can use the Google Cache: https://docs.google.com/viewer?a=v&q=cache:WCmq1ybmBqAJ:www.ussc.gov/Data_and_Statistics/Annual_Reports_and_Sourcebooks/2010/FigureC.pdf+&hl=en&gl=us&pid=bl&srcid=ADGEESilXv1aaDbX21Km_l4NgARe-6wI_aYmpDvcY9OMNMrayeLIJg-01o2tWEp1GeoYRgZ2pMXg7LkK5OQyI0q4ZDbArNevFiRd-nlp1q7MgMw-LO2C4LwopppI9RyzcLD9sopM3yeB&sig=AHIEtbR4psMUugvn_bV47GYdgak35_JkoQ https://docs.google.com/viewer?a=v&q=cache:WCmq1ybmBqAJ:...