They do provide some important information particularly when compared with other countries, technological developement and economic and political data. Factors like breakage are likely to be fairly consistent across the globe and periods in time, except wartime. The second level after the numbers are governmental reports which use the statistics but importantly, look at the trends of fashion, design and the impact of the different approaches to manufacture - sometimes at a remarkably detailed level. The trigger point for such reports often being International exhibitions and economic recovery following wars. When illustrated they tend to illustrate types of glassware being produced at certain periods and thus also become a tool in dating approaches. Such reports did have an impact on the industry. Political changes are a real fuzz factor for this as they can go against the trend in the reports with taxation being changed due to factors not related to the glass industry.
With a broad understanding of the above, analysis of the business of a single glassworks can be more completely assessed - a deeper understanding does, as Ivo points out, have little value to glass research per se.
But in respect of Bernard's original question - the statistics are useful as they do show the ratios of exports and has Bernard has noticed this does not compare well with his experience of glass in the collectors market from those areas. But this could be more fully understood with statistics, yet again. It needs to encompass demographic and migration as well as technology levels of the target countries. But such a study would be very time consuming... perhaps one of our visitors has a relative looking for a Phd subject

, alternatively someone with a strong interest and the skill set could almost certainly get a grant to do such a study :spls:
While statistics do not offer detail of the types of "Domestic and Fancy Glassware" in those market, the retailers and wholesalers in those countries did use photographs of their showrooms in adverts and while usually not clear enough in the screened advert photographs, they do at least give a good impression of what was being sold there. One such I have of a New Zealand importer known to import Monart, shows almost exclusively tableware with a small percentage of vases, some of which are just possibly Monart. Finding original photographs in company archives would be a lot more useful - these are spread around in libraries and museum reserve collections.