GDP measures the value of goods and services produced in the UK. The reading refers to a three-month growth rate, which is a better indicator of the underlying growth in GDP as the monthly figure is likely to be more volatile. In this sense, the monthly release can be thought of as a monthly update on three months’ worth of data on the economy, rather than a figure representing the economy in just one month. Rolling three-month data is calculated by comparing growth in a three-month period with growth in the previous three-month period, for example growth in March to May compared with the previous December to February.