The importance of design for the success of product innovations has caught increasing attention of scholars lately (Rindova and Petkova, 2007, Verganti, 2008). Previous research is related to user-centered design (Brown, 2008, Veryzer and Borja de Mozota, 2005a), design contribution to NPD (Gemser and Leenders, 2001, Talke et al., 2009), or design-driven innovation (Dell'Era and erganti, 2009, Verganti, 2009). Apart from few seminal contributions (Clark, 1985, Dell'Era and Verganti, 2007a, Walsh, 1996) research on product innovations has yet insufficiently investigated the relationship of functional (i.e. technology) and design dimensions (i.e. aesthetics, product language).Drawing on the literature of dominant design (Abernathy and Utterback, 1978, Murmann and Frenken, 2006, Suárez and Utterback, 1995), technological evolution (Dosi, 1982, Iansiti and Khanna, 1995, Saviotti, 1996) and innovation in design (Borja de Mozota, 2003, Verganti, 2008) we suggest that product design innovations are related to technical innovation patterns and characteristics of technology trajectories. Hence, we explore the relationship of design and technological innovations throughout the evolution of product categories. We argue that periods of incremental technical change trigger the cumulative development of design innovations, where both technology and design continue to develop along previously established trajectories. Contrarily, after periods of disruptive technical change that transform previously established product architectures into new industry standards, design innovation becomes increasingly important. Emerging dominant technological designs open opportunities for innovation in design and hence trigger periods where design features become essential for product diversification. Our explorative study builds on two pairs of meso-level case studies. Both, the technical developments of loudspeakers (Borwick, 2001) and bicycles (Dowell, 2006, Dowell and Swaminathan, 2006) are characterized by incremental improvements where the products architecture remained largely unchanged and thus product designs evolved along established paths. For instance, bicycles became stepwise equipped with increasingly complex suspension forks, gear systems and more efficient brakes but always maintained the original product architecture. Similarly, the quality of loudspeakers has increased continuously while they became cheaper to manufacture due to stepwise enhanced membrane materials and constantly improved bandpass filters. On the contrary, technical developments of watches (Glasmeier, 1991) and cameras (Carranza, 2010, Chandy and Tellis, 2000) are characterized by major, disruptive technological changes altering the products architecture that opened new design spaces for a variety of new product types. For instance, quartz watches allowed new designs due the replacement of mechanical clockworks. Also, the novel technical architecture of digital cameras enabled a range of new product designs (e.g. ultra compact or prosumer cameras). For our analysis we employ US patent data from 1970 onwards, using utility patents as proxy for technological and design patents as proxy for design innovations. To validate our findings we deepen our analysis with expert interviews from each industry and archival data. We contribute to previous research by deriving propositions on relationship of technology and design innovations. We propose that design innovation is stationary during eras of ferment, after technological discontinuities. Then, our findings suggest that the importance of design innovations increases strongly after the emergence of a dominant design, during the early stages of incremental change. In the later era of incremental change, we propose that incremental (cumulative) technology developments positively coevolve with continuous design developments.
