http://www.bea.gov/newsreleases/national/pi/2016/pdf/pi0716....
and GDP in current dollars was 18036.6 billion - http://www.bea.gov/national/xls/gdplev.xls, so 87.5% of GDP was income, and that figure has been pretty much constant over last 50 years, at never out of 75-90% range for sure. In fact, it is higher than average in the last 10 years or so - while difference is really small.
Disposable income after all taxes and including all social transfers (excluding non-monetary ones like food stamps and assisted housing) was 69.5% of the GDP, also quite typical figure which shows to tendency to fall over time, more likely to rise.
Surely that includes dividends, rents, and realized capital gains. And yet, it must have been reflected in the chart in question, if only in the top decile - while chart somehow shows incomes of all deciles falling from 2000, which is hard to believe.
Wage share is an economically accepted term, with data from BLS behind it.
You literally made up some number and said "it doesn't change much over time".
You're going to need to provide a source for that 80%.