Nearly all that we believe in surgery and nearly all that we practise is based on observational data, usually in the form of collected series.¹ Lung cancer surgery is no exception, and we rely—and will continue to rely—on the analysis of observational data. Observational research has tended to be denigrated and neglected.² There is currently a lack of broad based data of sufficiently high quality,³ so we welcome the Norwegian population based study reported by Strand et al in this issue of Thorax.⁴

The Scandinavian nations have been a great resource of high quality observational data and, in the BMJ alone, we have seen many community based,⁵ population based,^6–,⁸ and registry studies,⁸ of which those cited^5–,⁸ are a tiny but representative sample of the many submitted. Indeed, UK groups have been attracted to these databases for their own studies.^5,9 Scandinavian society has a number of features that seem, to outsiders at least, to provide a fertile environment for such studies. They have well developed healthcare systems with uniformly high standards and equitable access. Also, the populations are relatively stable—for example, only 13 of 3211 (0.4%) operated patients in the Norwegian study were lost due to emigration. Importantly, collection and analysis of data to inform policy is accepted in these countries as a right and proper function of the state. Strand et al relied on a population based cancer registry with obligatory entry by law, with no need for the patient’s consent, and which is automatically linked to the Norwegian Central Bureau of Statistics.⁴

Before discussing the results presented by Strand …