>The 2012 paper suggests that when private sector debt passes 100% of GDP, that point is reached. Another way of looking at the same topic is the proportion of workers employed by the finance sector. Once that proportion passes 3.9%, the effect on productivity growth turns negative.
Does not make any sense. Each economy is different, and the available data is probably not enough to give such accurate numbers.
>Ireland and Spain are cases in point. During the five years beginning 2005, Irish and Spanish financial sector employment grew at an average annual rate of 4.1% and 1.4% respectively; output per worker fell by 2.7% and 1.4% a year over the same period.
Using Spain as an example for "output per worker" is not a very good idea, they somehow broke productivity growth in 1994 and it's been stucked since then .
Productivity is affected by many factors, so conducting a ceteris paribus analysis is very complicated if not impossible. There is a really interesting book written by a journalist about productivity: The power of productivity 
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