BCN Ranking published an article called “Z mount suddenly rises to second place in interchangeable lenses, finally escaping from regular single-digit share“. Here is a quote from the article:
"However, it was Nikon's Z-mount lens for mirrorless single-lens cameras that increased its share from 5th place in June last year to 2nd place this June. It was revealed in the BCN ranking, which aggregates the actual sales data of about 2,200 stores nationwide, including consumer electronics mass retailers, camera specialty stores, and online shops. Z-mount lenses remained sluggish with a single-digit market share until February. Even in the sales ranking by mount, it was an unsatisfying 5th or 6th place. However, this March, he suddenly woke up. Achieved double-digit market share for the first time at 11.9%." (BCNRanking)
Next graph is Z-mount sales by manufacturer:
Note that the second-place ranking discussed above is for Z-mount in the interchangeable lens category. BCN Ranking collects real sales data from approximately 40% of the Japanese retailers - this is not a worldwide market share report. The latest mirrorless camera market share in Japan can be found here:
Sony fell from the top spot to the 7th place in the compact digital market in Japan
Via NikonRumors