I ran across this CPI calculator http://www.bls.gov/data/inflation_calculator.htm and decided to play with some numbers
Which is 47% less
Then I guessed 12% vs 40% Government spending from this table
and subtracted it from the average incomes.
Which brings me to the 64% figure.
Measures like this do not measure wealth. It doesn't matter how much money you make. What matters is what can you buy for it and whether what you can buy for it satisfies your wants more than in the past. I could argue that although people make less money they can have their needs satisfied better today. Amount of money you make is meaningless by itself.
The above is true. That's why figures like GDP do not adequately reflect living standards (because living standards are non-quantifiable and GDP masks hidden variables).
Still, the statistic you show is quite interesting. I have no idea what it means.