When you said 'national networks' what came to mind was countries like Norway, Finland, Sweden, Iceland, Denmark, Switzerland, Austria, and the like, where national networks not only have nationwide coverage, but very high ratings compared to their commercial radio sectors. And if you look at the populations of those countries, where national networks appear most successful, they range between 5-10 million (300K in the case of Iceland). Germany is about 90 million people, but the national radio network is divided into individual state radio networks.