Note: "\({\rm{l}}x\)" is the actual number or the proportion (as a decimal or percentage) of survivors at the beginning of age interval \(x\). Since several samples are often averaged together, the \({\rm{l}}x\) values may not always be whole numbers. "\({\rm{m}}x\)" is the number of female births to each age group of "mothers"; the number of eggs or young which are female (in a species with a 1:1 sex ratio, this is \({\rm{m}}x/2\) where \({\rm{m}}x\) is the total eggs or young produced per female at age \(x\)). Since, for most organisms, one male can fertilize a number of females, the size of the population is more dependent on the number of females present, and the calculations are usually done using only females.