There were only seven incidents in which control of air space sectors had been interrupted in the 22 months between January 2006 and October 2007, rising to a whopping 135 in the eight months since, he said.
How many controllers (on average) where on the payroll between Jan 06 and Oct 07.
How many controllers (on average) are currently on the payroll?
Do the number of controllers lost relate directly to the increase in incidents?
That should give an indication as to whether the increase is due to the number of ATC guys/girls or due to unofficial industrial action.