This research relates to digital software products and the firms that produce them. The approach used to explore these topics is that of modelling and computer simulation within the context of complexity cience. A complexity science approach advocates mapping equations from one research area to solve problems in another. In this case, the central features of the models are borrowed from the work of evolutionary biologist Stuart Kauffman. The research makes contributions to econonucs, strategic management and complexity science. It does so by creating a product centric model of software firms that provides an explanation of increasing returns and it backs this up with empirical evidence.