Even those from Gothenburg seem to take the train down to CPH to start trips out of CPH more than they go to ARN to start trips. So the CPH-originating catchment area has stretched up to around Gothenburg and also into Smalland since the bridge opened.
At CPH’s most emptiest in 2020, I had no problem repeatedly flying out of CPH when starting my days in Skane. That was even as the Danish police would stop me at times to make sure I was flying out of CPH rather than trying to play visitor in Denmark. There was about one week where things were unclear to me, but I always made sure to only use a regular US passport when crossing from Skane to CPH so I could get experiences of relevance to more people in Sweden wanting to use CPH to get out of Sweden (and Denmark) or back to Sweden, and I had no problems doing Skane-CPH-elsehwhere when Denmark was “locked down”. The Swedish government, regional figures and some critical businesses made it a priority that CPH would remain accessible for use by people/businesses in southern Sweden. But it was only that and CPH airport itself needing some Swedish workers that kept that option open for those of us starting the day by crossing the bridge to CPH.
Of course, there is a difference between statistics and estimates. Whether every second passenger with Kastrup as the final destination is actually going to Sweden or whether it is every fourth is a fairly significant difference that extends far beyond statistical margins of error.
Kastrup's geographical location in Europe is of course better than Arlanda's, nothing to say about that. What I want to say is that I do not agree with the claim that the number of air connections to Arlanda has to do with Stockholm's attractiveness to live in or establish a business in, and that Kastrup's passenger figures do not support such a claim either.
Stockholm’s attractiveness to business does matter for what routes work for airlines. And Stockholm’s attractiveness is worse than Copenhagen’s for that reason but also because of what kind of businesses it atracts and doesn’t attract. Want cheaper office space and place to have workers come in (and live or just stay using hotels)? With CPH, there is the choice of Denmark or Skane, based on what commercial and government partners have on offer. With CPH, there is also the superior business attractiveness related to cargo flows and other things. Stockholm is great, but from a business attractiveness perspective it struggles and is just not positioned to make ARN more important than CPH. We may like to blame SAS and Swedavia for this, but just think about the non-European airlines that have served ARN with long-haul service and then cut routes, down-gauged, or reduced annual flights from ARN and yet went more or longer with CPH . They cut on ARN because Stockholm was less attractive than Copenhagen for them. There are network effect benefits with CPH that just aren’t replicable with ARN.