The third competition called the M-3 Competition or M3-Competition (Makridakis and Hibon, 2000), was intended to both replicate and extend the features of the M-competition and M2-Competition, through the inclusion of more methods and researchers (particularly researchers in the area of neural networks) and more time series. A total of 3003-time series was used. The paper documenting the results of the competition was published in the International Journal of Forecasting in 2000 and the raw data was also made available on the International Institute of Forecasters website. According to the authors, the conclusions from the M3-Competition were similar to those from the earlier competitions.

The time series included yearly, quarterly, monthly, daily, and other time series. In order to ensure that enough data was available to develop an accurate forecasting model, minimum thresholds were set for the number of observations: 14 for yearly series, 16 for quarterly series, 48 for monthly series, and 60 for other series.

Time series were in the following domains: micro, industry, macro, finance, demographics, and other. Below is the number of time series based on the time interval and the domain:

Time Interval between successive observations Micro Industry Macro Finance Demographic Other Total
Yearly 146 102 83 58 245 11 645
Quarterly 204 83 336 76 57 0 756
Monthly 474 334 312 145 111 52 1428
Other 4 0 0 29 0 141 174
Total 828 519 731 308 413 204 3003

The five measures used to evaluate the accuracy of different forecasts were: symmetric mean absolute percentage error (also known as symmetric MAPE), average ranking, median symmetric absolute percentage error (also known as median symmetric APE), percentage better, and median RAE.A number of other papers have been published with different analyses of the data set from the M3-Competition.