When dealing with this kind of statistical distributions, it is important to refrain from pushing the analysis of the data too far and to stay at an appropriate level: a global analysis, rather than a case-per-case perusal - and this is especially true for the smaller samples.
If some of the surges or flattenings of the curves are clearly identified (WWI, WWII, beginning of space exploration, man on the Moon), others are less obvious (mid-seventies? mid-eighties?) and may be due to general economic fluctuations.
Two candid comments are however in order here: in order to issue some appreciation on the general development of astronomy-related activities, the curves displayed here should be compared with similar ones for other disciplines or even more globally for research - unavailable so far to our knowledge; also the rate of creation of astronomy-related organizations since the end of the fifties is really impressive - and there is no indication that this should still go on that way half a century later, especially at a time when the society at large has other priorities (health, unemployment, security, and so on) than space investigations or cosmological perceptions.
It is still too early to assess the real impact of the end of the Cold War (and of the subsequent reduction of subventions for fundamental research, including astronomy and space sciences). It might already be visible in the flattening of the curves in the nineties, but we believe that no authoritative conclusion is possible right now and that a similar study should be done again with more distance in ten or twenty years.
A category such as the software producers would of course not exist nor prosper without the advent of the computer age and the subsequent electronic networking of the planet.
The West European and the North American curves are mostly similar, but this is not always the case as illustrated in the previous sections.
Not surprisingly, the second oldest sample on the average is the "publishers'' one (and with the second largest dispersion), while the software producers constitute the youngest one (and with the smallest dispersion). The second smallest dispersion corresponds to the "planetariums'' sample (as explained above, an activity born roughly with this century), while the largest dispersion is achieved by the West European institutions, making up the oldest sample on the average.
We are very grateful to all persons and organizations who contributed over the past quarter of the century to the very substance of the master files used here by returning the questionnaires, by providing the relevant documentation, by participating in the various procedures of maintenance, validation and verification of the information, or otherwise.
Copyright The European Southern Observatory (ESO)