privateQueueMemory<Double>numberOfNonNulRecruitmentDuringLastYears;// Prob of non nul recruitment during the last "memorySize" years... if 10 non nul recruitment during the last 10 year, p=0.999... if 8 non nul recruitment during the last 10 years, p = 0.8... if 0 recruitment, p = 0.001