As of 2/22/2020, YFull v8.02, there were 523 samples from Germany. The national average for Germany is one sample per 157,000 people.

Three fourths of these people (390) identified a region within Germany.

Rheinland-Pfalz had by far the highest sampling rate. There is one sample on YFull for every 58,000 people in that state, almost triple the national average. Next is Mecklenburg-Vorpommern with one sample for every 101,000 people, which is about 50% greater sampling rate than Germany as a whole. None of the other regions have higher sampling rate than Germany as a whole.

Baden-Wuerttemberg comes third, with one sample per 128,000 people, followed closely by Saarland.

States with the lowest sampling rates are Berlin, Nordrhein-Westfalen and Hamburg. The lower rates could be due to the relatively recent growth of urban population centers in these areas since industrialization. Notably, Nordrhein-Westfalen includes the Rhein-Ruhr metropolitan area, the largest urban area in Germany and the third-largest on the European continent. It's possible that many of the people who have tested and currently live in these regions actually trace descent elsewhere in Germany.

The spreadsheet containing these figures, along with areas, can be found here.

I'm hoping these statistics may aid phylogeographical research. It may make it easier to detect regional patterns of samples indicative of Roman mediated migration vs other theories.