In 1999 the steerer broke on my bike at Lassay les Chateaux on the return from Brest. While I waited to get it sorted, I went into the cafe, where I chatted with some of the locals. One bloke said he wasn't into cycling, he was into football. That was the year after France's win in the World Cup.
In 2011 I went into the same cafe, during a DIY 200 during a visit a few weeks before PBP. I was curious to know what people did in these small towns and villages, and if there was much unemployment. The answer was that anyone unemployed move to the cities.
So I look at the small absolute decline in numbers of France PBP registrants, and I think about the relative success of the French football team, and French riders in the Tour de France, and it makes sense. Then I factor in the preference of St Quentin en Yvelines for the Ryder Cup over PBP, and it reinforces a sense of the shift away from cycling.
The growth in cycling in the UK makes sense, as we've become better at it. The decline in the USA is a fallout from Lance's disgrace.