Earned Schedule (ES) is an additional calculation for use with Earned Value. It’s neither difficult nor time consuming. It’s not that new either, having been used informally since the early days of earned value.
The theory, technique and calculation has been formalised by Walt Lipke. Kym Henderson validated the technique and extended its use to forecasting using current projects in the USA, Australia and the UK since 2003. The ES technique has also been validated by using data from projects already completed (and in some cases, cancelled) both in the public and private sectors. Research is still ongoing to validate the use of ES – the evidence suggests, so far, that this is better than ‘organic interpretation’ - also known as guesswork - but not necessarily better than using existing EV reporting techniques to their full potential. Both real and simulated data has shown the ES technique to be more accurate when compared to other predictive statistics.
It is, in essence, an extension to Earned Value and another project control technique to be used in conjunction with existing methodologies. The most important development in ES is its ability to more accurately determine the completion date for projects that are behind schedule (or will deliver later than planned.) ES uses EV performance data to generate the time-based information and as with EV, uses very similar calculations to predict future performance. Earned Schedule can be used to “drill-down” through the project’s Work Breakdown Structure (WBS), in much the same way as Earned Value, to identify where deficiencies or constraints may exist and where future rework may be needed, if current performance does not change.