Many are talking about the bond market being the latest bubble. But it looks more like the press is just seeing bubbles everywhere. To me a bubble happens when everyone starts believing something that probably is not true. For example in the 1990′s investors started thinking that the long term earnings growth of the S&P 500 was shifting up from its long term 7% growth rate. So they believed that the market was worth more than historic valuations implied and the market PE rose to the 25 to 30 level.
In the 2000′s bankers and home owners came to believe that housing prices could never fall so that homeowners could always refinance their mortgages. Consequently, lenders did not have to worry about credit risk.
So for the bond market to be a “bubble” investors would have to start thinking they can make unusually large capital gains in the bond market. But everyone knows that if you buy a 10 year bond that at the end of 10 years all you will get back is your original investment. In the meantime you will get the coupon and what you can earn by reinvesting that coupon. Yes, if rates continue to fall in the short run you will be able to sell the bond for more than you paid, but you total return has to remain limited because in 10 years the possibility of capital gains must converge on zero. As long as this is true the possibility of a bond bubble must remain something reporters and pundits can pontificate on but nothing more than that.