The 50's were all over the place but on average it was around 2% - I guess it was close to being the same as now.
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I have no idea if this is a valid site for calculating inflation rates relative to other eras, but I found this site, in which it seems $100 USD in 1954 is equivalent to $859.91 USD today.
Inflation Rate Calculator- from InflationData.com
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That's what I'm doing now.