Forecasting ≠ Estimating
In the book on #NoEstimates, it is stated the difference between estimating and forecasting using a Merriam Webster dictionary. This book states estimating is "giving a general idea about the value, size, or cost of something". Forecasting, on the other hand, means "calculating or predicting some future event usually as a result of analysis of available pertinent data". The important difference is that the latter one uses data when the first one does not.
This is a prime example of cherry picking a definition to suit the needs of the author. What is needed is to Not Use the Word Estimate, when in fact Forecasting and Estimating are the same process, just different means, and time frames.
Let's look at a more reliable source for definitions in the project management domain. Project Management Institute's PMBOK 5th Edition all the way back to the 3rd Edition
- Estimate - A quantitative assessment of the likely amount or outcome. Usually applied to project costs, resources, effort, and duration and is usually preceded by a modifier (i.e., preliminary, conceptual, feasibility, order-of-magnitude, definitive). It should always include some indication of accuracy (e.g., ± x percent).
- Forecast - An estimate or prediction of conditions and events in the project’s future based on information and knowledge available at the time of the forecast. The information is based on the project’s past performance and expected future performance, and includes information that could impact the project in the future, such as estimate at completion and estimate to complete.
So Forecast is an Estimate based on information available at the time of the forecast
It is a fallacy to say
Forecasting is not estimating, therefore we can make forecasts in the #NoEstimates vernacular and not call them estimates
