A growth model for the quadruple helix

<title>Abstract</title> We develop a R&D-based growth model with productive public expenditure in order to frame the Quadruple Helix (QH) innovation concept, based on four helices: <italic>Academia & Technological Infrastructures</italic>, <italic>Firms</italic>, <italic>Government</italic> and <italic>Civil Society</italic>. Our motivation stems from acknowledgment that the relationship between these four helices and their joint impact on growth is in need of a theoretical framework. We aim to emphasise the importance to economic growth of innovation systems structured on these four helices. The introduced model confirms theoretically the notion that increases in: (i) complementarities between distinct productive units, or (ii) in productive government expenditure, lead to higher growth.