Its not a fluctuating rate issue as much as a function of Spain breaking itself down by localities and downstreaming their governance. Starting when Spain moved from dictator Franco to constitutional democracy in 1978, it broke itself up into 17 Autonomous Regions. The income tax rates charged actually differ from one region to the next. A Madrid resident has a lower income tax rate than someone living in Barcelona. 15 years ago or so, each region also took over its own tax collection and enforcement.
This Shakira case is triggered by her long term live in/children with Gerard Piqué of Barcelona FC, which broke up, and she's left town. You may recall another Barca star Lionel, also had a "Messi" tax case. He settled and he also left town. Both cases emanate from Barcelona, Autonomous Region of Catalonia.
Two theories on these cases :
1) the crazy Catalans believe aggressive high profile prosecutions like this serve to chill/deter tax avoidance by others.
2) Barca is the GB Packers of futbol. Democratically run by the regular vote of the stakeholders..its been the socialist team to Real Madrid's history rep as the facist team favored by Franco. The Barcas will pay the big bucks, but insist the social aspect of tax payments on the big bucks are met, especially on carpetbaggers from Columbia and Argentina, like these two.
Its probably a little of both, but mainly grandstanding by those crazy Catalans.
For a flavor of the separateness of this area watch Dos Cataluñas on Netflix.
