No, it is not related to an overloading of the social security system in that way. Yes, the system is overloaded by having a large new contingent of non-contributing individuals partaking of the payouts but this has not led to a decrease in those payouts, far from it. A family with 5 children can get enough money from the state - in 2016 the amount was 32.800 kr according to a calculation published by Riksdagen (the Swedish parliament) which comes down to a lower middle class income - for a reasonably comfortable life without ever having to seek employment.

The problem is cultural, not economical. The Swedish state has, following a decision pushed by Olof Palme on Sweden having to become 'a multicultural state like the United States of America where Swedish culture is no longer the single dominant one' followed a policy to not only allow but encourage migrants to not integrate or assimilate into Swedish culture but to keep and strengthen their own, paid for largely by the Swedish state through subsidies for ethnically segregated cultural organisations. This has led to the establishment of ethnically segregated areas in many of the larger cities with names like 'lilla Mogadishu' (little Mogadishu), 'lilla Kabul', 'lilla Bagdad' and more. It has led to objectively unexplainable situations where a regime-supporting Eritrean cultural festival is organised in Stockholm by "refugees" from the same regime which then attracts opponents to the regime from all over Europe who come there to make war on those same regime-supporting "refugees" [1]. It has led to parts of Göteborg - the second largest city in Sweden - being under the virtual control of the Ali Khan clan [2] with members erecting road blocks to keep out authorities, somewhat comparable to the way road blocks were erected in Portland OR but far more established than those temporary eruptions of anarchy.

Sweden is now a cauldron bubbling with different factions - Afghans, Somalians, Moroccans, Iraqi, Syrians, Turks, Lebanese, Ugandans, Eritreans and more - striving for dominance in different types of organised crime. The multicultural 'experiment' has failed spectacularly and disastrously as was foreseen by many but which was not to be spoken of in fear of being labelled a 'racist' or 'nazi'. This labelling still continues and the denial still prevails but the subject has become more approachable due to the fact that the results of this failure are clearly and undeniably visible for anyone to see. What remains is to find a solution for the problems caused by the near half century of mismanagement and misdirection which keeps those aspects of Swedish culture and society which made it successful and worthy of emulation but does away with the ideologically driven mistakes. Given that the political party most (but certainly not solely) responsible for these failures - Socialdemokraterna or "the social democrats" - is and has for a long time being the largest and most dominant party combined with the fact that political parties in general and this party in particular are not known for admitting to past mistakes it remains to be seen whether and if so to what extent this will happen.

[1] https://www.tv4.se/artikel/3qmMWIhaUax7HuAl2mQxOF/kaos-vid-j...
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[2] https://sv.wikipedia.org/wiki/Ali_Khan-klanen