Final answer:
The Schedule Performance Index (SPI) is the indicator that reflects the efficiency of the project's progress compared to its original planned costs and schedule.
Step-by-step explanation:
The metric that is based on the original planned costs for the project or activity and the rate at which the team is completing work on the project or activity to date is the Schedule Performance Index (SPI). The SPI is a measure from the earned value management methodology that indicates how efficiently a project is progressing in terms of its schedule. An SPI value greater than 1 suggests that the project is ahead of schedule, while a value less than 1 indicates that the project is behind schedule.