One reason for avoiding judgemental FORECASTS is that, in many cases, they are more expensive than quantitative methods. If it is NECESSARY to make inventory CONTROL forecasts every week each of 50,000 items, judgment cannot be used. Another reason for avoiding judgmental forecasts is that they are usually less accurate than formal methods. RESEARCH has shown that judgmental forecasts are subject to many biases such as optimism and overconfidence. Nigel Harvey (2001) describes how to OVERCOME many of these biases. If you need convincing that credible experts often make abysmal forecasts, see Cerf and Navasky (1998). For example, John von Neumann in 1956 said “A few decades hence, energy may be free - just like un-metered air.”

One reason for avoiding judgemental forecasts is that, in many cases, they are more expensive than quantitative methods. If it is necessary to make inventory control forecasts every week each of 50,000 items, judgment cannot be used. Another reason for avoiding judgmental forecasts is that they are usually less accurate than formal methods. Research has shown that judgmental forecasts are subject to many biases such as optimism and overconfidence. Nigel Harvey (2001) describes how to overcome many of these biases. If you need convincing that credible experts often make abysmal forecasts, see Cerf and Navasky (1998). For example, John von Neumann in 1956 said “A few decades hence, energy may be free - just like un-metered air.”