I would imagine with the consistent number of people going through the training system every bid period there is a similar number of eligible voters who are leaving short haul.
As the year’s training is allocated in 1 hit prior to the start of the training/financial year you’d have a number of pilots who know they are leaving that year and may want the E.A. sorted before they leave.
Every month that goes by the number of pilots who know they are leaving later that year decreases until all have commenced training. The pipeline doesn’t get replenished until June the following year.