My personal advice: Don’t!*
But Lee Siegelman relays some results from a US study into completion rates among Ph.D.-students in Political Science and asks:
For example, what is it about political science as a field of study that slows our students down relative to the performance of students in some other social science disciplines? (The fact that many of our students do extensive fieldwork obviously enters in, but there must be more to it than that.) What, for that matter, is there about the social sciences that slows our students down relative to the performance of students in most other fields (the obvious exception being the humanities)? And what can political science programs legitimately do to move our students along at a less glacial speed, especially given that most programs provide funding for no more than five or six years?
I don’t have any Scandinavian numbers (at least not at hand) but my hunch is that this doesn’t necessarily apply to Scandinavian universities. The Swedish problem generally used to be that post-graduate education wasn’t linked with financing so departments would take on applicants beyond their – and the applicants’ – capacity. In Denmark, organised post-graduate programmes (i.e. beyond the 5-6 year kandidat-degree) is a relatively new phenomenon – I actually belong to some of the first cohorts of Ph.D.s.
And in case you wonder, I wrote my Ph.D. dissertation in a little over two years – due to (lack of) financing of the programme I was involved in. This was definitively not an experience I would recommend to anybody, but fortunately things have been straightened up somewhat since the early 1990s.
*Why not? 1) I have no indications that holding a Ph.D. in Political Science will be an advantage over holding an PolSci M.A. on the general labour market (a Ph.D. in economics or statistics may be useful, though) in Scandinavia, 2) the academic labour market is limited and pretty bumpy. So you’re turning away from the high road and into a pretty much unchartered field full of the proverbial dragons. If, on the other hand, you are the adventurous type, then a PolSci Ph.D. may be something for you.