The process of cleansing historical data is a manually intensive and unproductive process, in my opinion. In fact, in all my years of doing demand forecasting, the only time historical demand data were changed (corrected) was if the data were entered into the data warehouse incorrectly, or if the historical data needed to be restated due to distribution warehouse consolidation. Many companies continue to manually cleanse their historical demand data as a prerequisite for forecasting and planning of their products. It is a manually intensive process that takes up in many cases 80 percent of a demand planner’s time. The true reason for cleansing historical demand is that traditional demand forecasting and planning solutions are unable to predict sales promotions or correct the data automatically for shortages or outliers.

From Issue: Five Trends That Will Impact S&OP Over the Next 10 Years
(Fall 2016)

Does Demand History Really Need To Be Cleaned?