A count of how many pull requests are merged over a period of time.

Each pull request represents a unit of work that has been perceived as having some value by the engineer who submitted it (e.g., implementing a feature, fixing a bug, or improving a part of the code base). Thus, a total count of merged pull requests can serve as a proxy for value delivered. 

Over time, this metric signals whether your engineering organization is getting more or less productive. This long-term understanding of output and the direction it’s trending helps you see whether changes to the team are having the expected impact. 

Pull Request Throughput can be used as a success metric that communicates progress both within and without the engineering department. 

Note that this metric is not diagnostic, so to identify why throughput is low, you’ll want to look at metrics that make up smaller components of the software development process, such as Time to Open, Time to First Review, or Time to Merge.