Use of the Term: Per Capita Births per year in the model with 'Carrying Capacity' added
Note that the right-hand-side of the equation:
Births per year = Per Capita Births per year * Population * (Carrying Capacity - Population)
doesn't quite make sense, in contrast to the right-hand-side of the equation in the previous model:
Births per year = Per Capita Births per year * Population,
which does make sense. Per Capita Births means the number of births per person. Multiplying births per person by the number of persons (the population, that is) gives the number of births. So, Per Capita Births * Population is the number of births and Per Capita Births per year * Population is the number of births per year. Putting in the additional factor (Carrying Capacity - Population) messes up the balance.
Since Per Capita Births per year * Population gets multiplied by another number of people: (Carrying Capacity - Population), the converter Per Capita Births per year should actually have yet another 'per' and be called something like
Per Capita Births per year per person,
where this 'person' refers to one of the theoretical people making up the difference: (Carrying Capacity - Population)! Because this parameter is the number of births per capita per year per person, its value should be quite small.