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.