Long Productivity

The productivity being measured here is specifically *labor* productivity..am I correct? It would be interesting to see trends on the productivity of capital assets, as well.

Yes, it's labor productivity. Interestingly enough, capital productivity has been falling since the mid 1960s, but the rate of decline has decisively slowed in recent years.

20 year growth rate of capital productivity
period ending
1972 -0.1%
1982 -1.2%
1992 -1.1%
2002 -0.3%

I have been trying to calculate productivity at the state level. So far Real GSP/Employment seems to work the best. This puts productivity in terms of average value of output per employee. This number is low because GSP excludes federal employee compensation, but they are included in employment. The annual average weekly hours data is not available for total employment so it is impossible to convert to output per hour at the state level. It is interesting to rank GSP per employee by state.

How much of this is demographics, say the population of 35 to 50 year olds when people are more skilled in their careers?

I would think that something like a 50 year chart would be more informative. It would show that the 1975-95 slowdown was the exception, not the rule. Moreover, the recent productivity miracle is just a rebound to historic norms.