computer implemented method and system for improving demand forecasting by estimating the hidden demand at an occurrence of a sellout using a single parameter probability distribution with a parameter assuming a forecasted mean demand value derived from a statistical seasonal causal time series forecasting model of count data on a new data set of sales values excluding truncated sales values at occurrences of sellouts . the present invention also provides for new more accurate performance evaluation techniques together with new performance metrics for evaluating an actual draw and for comparing a recommended draw to an actual draw .