Drawing on a large database of publicly announced R&D alliances, we track the evolution of R&D networks in a large number of economic sectors over a long time period (1986- 2009). Our main goal is to evaluate temporal and sectoral robustness of the main statistical properties of empirical R&D networks. By studying a large set of indicators, we provide a more complete description of these networks with respect to the existing literature. We find that most network properties are invariant across sectors. In addition, they do not change when alliances are considered independently of the sectors to which partners belong. Moreover, we find that many properties of R&D networks are characterized by a rise-and-fall dynamics with a peak in the mid-nineties. Finally, we show that such properties of empirical R&D networks support predictions of the recent theoretical literature on R&D network formation.
