Bottazzi and Peri (Economic Journal 2007; 117: 486–511) show the existence of a cointegrating relationship between the domestic stock of knowledge, domestic R&D and the international knowledge stock for a panel of OECD countries and interpret it as evidence supporting the semi-endogenous versus the endogenous growth theory. We replicate the baseline specification of their study and we show that main results are robust to the use of a different estimation strategy (Bai et al., Journal of Econometrics 2009; 149: 82–99) that duly takes into account cross-sectional correlation: interestingly, in this case we also find a larger role for knowledge spillovers. Copyright © 2014 John Wiley & Sons, Ltd.