In article ,
Thomas Borchert wrote:

John,

Germany lists about 20000 registered aircraft(imagine that half that
number is parked at OSH each year), including over 7000 sailplanes and
6700 SEL.

The registered aircraft numbers can be deceiving.
In the USA for example, there are many aircraft that remain on the
active registry, but are in various stages of
assembly/disassembly/airworthiness.
As a result, post 9/11, the FAA has tightened up on the accuracy and
requires a confirmation of status every three years.