taw:

Inflation-adjusted US treasury bonds have rates like 1.68% a year over last 12 years., and never really got much higher than 3%.

Not to mention that even these figures are suspect. There is no single obvious or objectively correct way to calculate the numbers for inflation-adjustment, and the methods actually used are by no means clear, transparent, and free from political pressures. Ultimately, over a longer period of time, these numbers have little to no coherent meaning in any case.