After I copied all cars specifications from German automobile club into Excel format, I analyzed it to show you how cars sold in Germany evolved over past 50 years (this analysis apply for whole Europe, 99% of cars sold in Europe are also sold in Germany). I calculated using AVERAGEIFS formulas. Charts made at 18 September 2019 update with 122214 model versions. You can buy Excel database: German Car Database.
In case of American car database, there is a row for each “Model Year” a car was sold in, so each year calculate average data values of cars available that year and the evolution looks constant. But in case of Europe, the statistics are based on the year of launch, so there are large variations in average data values from one year to another, for example in 1970 a large number of small cars are launched, and in 1971 a large number of big cars were launched. Only after 1975 number of cars launched per year included in database is high enough to reduce variations of average values, but still do not make a constant evolution.