Almost certainly coincidence, but just a fun fact... I was looking at the male/female firing ratios in the various weeks, and the one that stands out the most is that in almost all of the series, a woman has been fired (or left, in the case of Series 1) in the fourth week. The only occasions when this hasn't happened have been with Simon in Series 4 and Lewis in YA2.
) and it's certainly a funny coincidence.