During the last decade High-Growth Firms (HGFs) – often referred to as ‘Scale-Ups’, have become increasingly recognised as important by policy makers. We know relatively little about the

dynamics of these firms as they evolve over time. This paper develops a measurement framework designed to track the population of high growth firms (HGFs) between 1998 and 2015 using ONS data, building a simple model of the evolution of the HGF population.