I don't really see the point, your research will be deviated by factors that would influence a study such as you mention.
Of course you will find smaller pens still sell more, they are cheaper... on average (again - we already said there are some cheap pens that are large...). This has deviating effect on sales that will false your comparison.
(stick to fountain pens however, ball points are another matter, I actually don't consider them to be "pens").
Of course the MB149 was there 70 years ago (it was launched in 1952 if I'm not mistaken) and so were other large pens like the Duofolds
but on average, look at the market then, and the market now, it's clear there are more larger pens around now.
I'm not trying to say anything different from this, but I don't think you need statistics to see that either.
Since it's not my intention to deviate from the topic further, I confirm that despite it's smallish size by today's standards the Pelikan 101N and M101N is an extremely nice pen which does fascinate me much more than a MB149 (which I don't have) and gets much more use from me than the MB146 (which I do have).