Car classification in Europe is not officially regulated, instead, it is defined in relative size with other cars.
Today the average lifetime of a car model is 6 years for compact and medium cars and 8 years for mini and luxury cars. Is normal for cars to grow over years, as technology advance and more gadgets should be included under body, but in Europe since 1990s, the cars are growing crazy with about 10-20 cm per model change, which is exaggerate, based on technology evolution, 5 mm per year is enough. This non-natural grow causes companies to abandon large models and introduce new smaller models below existing models.
Some brands do not follow the common class sizes, making cars with intermediate sizes, these are usually considered being part of the smaller class, causing further increase in size of car classes.
Seems that all European companies wants to make a car bigger than competitor’s cars of same class. This leads to 2 cm / year increase in average car length in each class. The cars get fatter also in width, this is an issue for parking design, since in most countries the parking lots are 2.5 m width, most compact cars were under 1.7 m width in 1998 but since 2008 most are over 1.8 m.