It seems that trying to distill the activity of 7+ billion people into a line graph that you can extend naively to make predictions is a bankrupt exercise. Calling lower-than-predicted growth a slowdown is more than a bit disingenuous.
Derivative of productivity != productivity, NYT.
See, this is what happens with decades of people tolerating media confusion between the GDP and the annualized rate of growth of the GDP.
Now its spreading to everything else.
Yeah, it's slightly disingenuous, but we still need some models. It's like when people take the total revenue of Google and divide by the total number of Google employees (including assistants and chefs and tech support and the PMs and artists and designers and all the actual engineers too) to reach a "revenue per employee" number.
It's not perfect by any means, but anytime you divide one number by another, you get to call your result a metric (then you get to write insights about your new discovery too).