[tovej]

My thought was that it would be interesting to look at such timeseries data for discontinuities that you could correlate against historical events to get some insight into the impact of policy decisions, and the development of neoliberal capitalism.

The plateau at 30% (assuming it is a plateau) seems reasonable. Unless goods are counted twice, a stable upper limit is clearly 50%, as firms output something eventually, and presumably the value of the goods never decrease in the value chain.