well, Japan have like 6 WD pairs to compete for title every tournaments.Thanks for creating this statistics. I initially thought something off in your statistics until I realized that BWF Tour 100 isn't included in the statistic.
Looking at the statistics, Japan is really strong at WD category. Japan's domination in WD is better than China in XD and Indonesia in MD.
well, Japan have like 6 WD pairs to compete for title every tournaments.
both CHN and INA have like two title chalenger pairs for its category