For example, the Lehman Aggregate Bond Index contains more than 6, 000 bonds, but the Barclays iShares Lehman Aggregate Bond Fund ( AGG) contains only a little more than 100 of those bonds.
Over the past decade or so, the worst loss suffered by Lehman's Aggregate Bond Index (amex: AGG - news - people ), a proxy for the entire bond market, was a 3.5% decline over two months in mid-2003.