During the Second World War, most developed countries, whether belligerent, occupied or neutral, introduced rationing and price controls. The prescription of a centrally designed pattern of consumption (and expenditure) for most or all goods led to the flourishing of shadow economies. Both during and after the war, governments and other authorities have mostly depicted black markets as products of selfishness and decadence, as criminal delis where the rich and ruthless had their fill at the expense of the nation and its people.
While this image is not as such untrue, it is certainly incomplete. In both the Danish and the Dutch case, I have been able to establish that the poor, and notably the urban proletariat, used black markets to adapt their buying rights to their limited purchasing power. Black markets were not only indicative of the luxurious tastes of the well to do, but also of the limitations of economic control and the economic inequality that persisted throughout the 1940s.
"Income, Class and Coupons. Wartime Black markets for Food in the Netherlands." in: Food and History 8 no.2 (2010).
(with Claus Bundgård Christensen), "Zwarte markten in de Tweede Wereldoorlog. Een vergelijking tussen Nederland en Denemarken." In H.A.M. Klemann and D. Luyten (eds.), Thuisfront. Oorlog en economie in de twintigste eeuw: Veertiende jaarboek van het Nederlands Instituut voor Oorlogsdocumentatie. Meppel: De Walburg Pers, 2003.