The CPI (used to gauge inflation) has been modified in a variety of ways over the past 35 years. Various estimates of what the annual rate would have been over the past four years if earlier methods of calculation had been continued come up with numbers in the 5%-to-10% range.
http://business.time.com/2013/03/12/if-theres-no-inflation-w...
http://www.bls.gov/cpi/cpiqa.htm#Question_5
Its a variance of less than 00.3% due to methodology changes. I understand its a popular myth.
Please provide a source that accurately copies the methodology from the 1970s and agrees with your claim.
If you are unable to do so without citing Shadowstats or another source that wants money to see their full methodology, its an invalid claim intended to milk money from people with fixed belief systems.