"More of ... than"

Question

In the early 1950’s, historians who studied preindustrial Europe (which we may define here as Europe in the period from roughly 1300 to 1800) began, for the first time in large numbers, to investigate more of the preindustrial European population than the 2 or 3 percent who comprised the political and social elite：the kings，generals, judges, nobles, bishops, and local magnates who had hitherto usually filled history books.

In the sentence above, what I do not understand is the part "to investigate more of the preindustrial European population than the 2 or 3 percent who comprised the political and social elite"; specifically, how to comprehend the "more of... than"?

Answer 1

Whenever you have than, you have a Comparative construction. Than only occurs in comparatives, and comparatives are very peculiar, complex constructions, containing more (or less for negatives, or the suffix -er for shorter words) as well as an optional baseline comparison introduced with than:

• His list has bigger bullets than hers does.
• His list is more important than hers is.
• I like her list better than his.
• There are more points on her list than on his.
• More of his list is boldfaced than hers.

Various repeated parts of the baseline comparison constituent (a clause or a phrase) may be deleted and often are, like hers standing for her list, or is standing for is important. These two constituents -- the causative constituent and the baseline comparison constituent -- can occur, as one can see, just about anywhere in the sentence, and in many other constructions, though the comparative more/-er constituent has to come before the baseline than constituent.

The than constituent, incidentally, is a negative trigger, generating NPIs like ever and anybody.

• He's even faster than anybody expected.
• He's faster than I ever expected.

Answer 2

More here is a fused determiner head - the noun it determines has been left out, and in this case has to be inferred, not taken directly from context. This is because the than... part of the comparative construction has percent as the term being compared, which is incompatible with more:

*more percent of... than the 2 or 3 percent who comprised...

So we have to interpret it something like:

a greater percentage of... than the 2 or 3 percent who comprised...

It could be reworded as:

...to investigate a percentage of the preindustrial European population greater than the 2 or 3 percent who comprised the political and social elite...

Answer 3

More X than Y is a standard construction. It makes a comparison between X and Y.

"to investigate more [= a greater amount] of the preindustrial European population than [=in comparison to] the 2 or 3 percent (of that total population) who comprised the political and social elite";