Interestingly, 3% was the magic number that helped break the global economy in 2008 according to Planet Money: https://www.thisamericanlife.org/355/the-giant-p

Interestingly, 3% was the magic number that helped break the global economy in 2008 according to Planet Money: https://www.thisamericanlife.org/355/the-giant-pool-of-money https://www.thisamericanlife.org/355/the-giant-pool-of-money In short, finance professionals looking for reliable 3% annual returns could no longer count on US treasuries to help get them there so they turned to securitized mortgages.