1. A method to determine demographics for non-panelist households, and reduce a quantity of panelist data retrieved from a computer memory, the method comprising: reducing, by executing an instruction with a processor, the quantity of panelist data retrieved from the computer memory by calculating a first demographic constraint average and a second demographic constraint average in connection with tuning events of non-panelist households, the first and second demographic constraint averages based on (a) acquiring a first quantity of temporally-mapped panelist demographic distribution data occurring during and associated with a first tuning event of a set-top box of a respective one of the non-panelist households and (b) acquiring a second quantity of temporally-mapped panelist demographic distribution data occurring during and associated with a second tuning event of the set-top box of the respective one of the non-panelist households, the first and second tuning events of the non-panelist household reducing a quantity of the first and second temporally-mapped panelist demographic distribution data retrieved from the computer memory, the first quantity of temporally-mapped panelist subset of demographic distribution data including (a) a first probability that the first tuning event is associated with a first demographic constraint and (b) a second probability that the first tuning event is associated with a second demographic constraint, the second quantity of temporally-mapped panelist demographic distribution data including (a) a third probability that the second tuning event is associated with the first demographic constraint and (b) a fourth probability that the second tuning event is associated with the second demographic constraint; based on the first demographic constraint average and the first probability that the first tuning event is associated with the first demographic constraint, determining, by executing an instruction with the processor, a first likelihood score of the non-panelist household being associated with the first demographic constraint; based on the second demographic constraint average and the second probability that the first tuning event is associated with the second demographic constraint, determining, by executing an instruction with the processor, a second likelihood score of the non-panelist household being associated with the second demographic constraint; estimating, by executing an instruction with the processor, a household characteristic of the non-panelist household based on the first likelihood score and the second likelihood score, the household characteristic including a number of members of the non-panelist household; and producing, by executing an instruction with the processor, ratings of presented media for a mixed audience of non-panelist and panelist households based on the household characteristic.