What does a SPI value less than 1 indicate?

A Schedule Performance Index (SPI) value less than 1 indicates that the project is progressing slower than planned. The SPI is a measure of the efficiency of time used on a project, calculated by dividing the earned value (EV) by the planned value (PV).

When the SPI is less than 1, it signifies that the earned value is less than what was planned for that point in the project timeline. This means that the work completed is behind the planned schedule. Therefore, a SPI value of less than 1 serves as an alert that corrective action may be required to bring the project back on track. It emphasizes the necessity of closely monitoring project timelines and schedules to ensure timely completion.

The context helps to understand that while the other options may relate to project performance, they do not accurately describe the implications of an SPI value of less than 1 as effectively as this one does.