The document discusses metrics that are used to measure the performance of NHS library services. A survey was conducted to understand the types of metrics currently in use. The most commonly reported metrics involved usage data for resources like e-journals and databases, as well as turnaround times for document delivery and literature searches. Cost per download was also widely cited as it can be used to inform decision making and demonstrate value. The variety of metrics indicated that services are looking for ways to show their impact, satisfy stakeholders, and gain insights into user behavior.