The figure comes from a series of phone calls to the major hive manufacturers in the UK asking them approximately what percentage of the different types of hives they sold. The figures were all approximate but broadly speaking they were the same between the various suppliers. Approx 90% Nationals, 5% Langstroth and the remaining 5% were a mixture (smith, dadant, TBH, Warre etc).
Fair enough, it's a recent survey of what the largest UK manufacturers say they sell. A few problems with linking that as equal to the number of hives in the UK though.
Th0rnes used to claim WBC was their second best selling hive, and 14x12 is increasingly popular. The numbers might make sense if 90% covered all the national frame based variants, even Dartington and Beehaus. But to claim that a WBC hive is the same as a National, same as a Beehaus is stretching the category a bit.
The number of hives sold at any point recently takes no account of how many were sold in the past and are still in use. There are many elderly Nationals and Commercials still in service. And many of them are home made or from a local wood worker. Commercial brood boxes were certainly more popular locally, you're probably underestimating them.
TBH, Warre and a few other types are going to be mostly home made. There are a few old models still going and foreign specialities personally imported, such as French Dadant Blatt or Eastern European long hives.
A good number of langstroths are used by the largest operators. They usually import directly and if ITLD is typical, the recent ones are probably poly langstroths from people like Swienty or Lyson. They also import frames directly so don't figure in any UK supplier estimates.
There are quite a few smaller suppliers who stock European poly hives, mostly langstroth. Not manufacturers as such but supplied and used in the UK.
You might find some approximations partly cancel each other out, older Nationals increase the percentage while direct imports of other formats decrease it. But there's no ovious way of estimating the correction either way. My guess would be that many go to big manufacturers for wooden nationals, but their sales underrepresent other formats in use.
