To give one example of the potential value of the links between VD16 and the
PND GND (about which, see
here for more), let's take a quick look at printing of works by authors of classical antiquity in Germany in the sixteenth century. The classics were an important part of the market in printed books, and there has been a good amount of research on it.
To get an overall view of the market working just with VD16 would be arduous, however. You would have to identify all the relevant authors and then search for titles by each one. If you're determined to try it, you should expect to spend many days at it.
An easier solution would be to search instead for titles whose authors have a death date before, say, 200 A.D. With the VD16 data linked to the GND, we can do that. Authors who died before 200 are almost entirely limited to Greek and Roman authors of classic literature rather than patristic authors, and excluding "Personen zu Kirchengeschichte" will eliminate the exceptions.
Here's a graph of the results.
Printed titles by authors of classical antiquity per year, 1501-1600
There are clearly some visible patterns, but the data is noisy, and we're suspicious of all those spikes on even decades, so let's smooth out the picture a bit by looking at production by half-decades instead.
Printed titles by authors of classical antiquity per half-decade, 1501-1600
Things look pretty stable after 1525, but the big run up to 1520 and then the steep drop over the next five years looks interesting. When we see something like that happening in German printing, a good guess is that the Reformation is behind it. Did Martin Luther kill off the market for Cicero, the most popular of the classical authors between 1501 and 1520? Perhaps for a while. Cicero editions peak at 94 per half-decade in 1516-20 and then decline to half that number before recovering by 1545. (The first two graphs count editions in slightly different ways than this one does, so there may be discrepancies between them.)
Printed titles by Cicero per half-decade, 1501-1600
This all comes with a few caveats, of course. If the GND is lacking a death date for a relevant author, our search will miss him or her. And the precise mechanism through which an increase in Reformation-related printing would cause a decline in editions of classical authors remains murky at best. On the other hand, it only took a few minutes to see some initial results rather than a few months, and it points towards some interesting areas to look into.