A method is provided for detecting when users are being adversely impacted by poor system performance. A system health indicator is determined that is based on the amount of work that is blocked waiting for each of a set of an external events and combined with a heuristic that is based on the number of users waiting for the work to complete. The system health indicator is compared to a threshold such that an alert is generated when the system health indicator crosses the threshold. However, the system health indicator is designed so that an alert is only generated when a significant user base is or will in the near future experience a problem with the system. Furthermore, the system health indicator is designed to vary smoothly to maintain its suitability for the application of predictive technology.