A question about history

So I was reading on Wikipedia about empires.

And their article states that the roman empire was larger than Nazi Germany. In square KM, 6.5 to 6.4, which seems believable. But also in population, at 80 million to 75.4 million.

I have a hard time believing this. The land controlled overlaps to a fair extent. That would seem to indicate that the population density in 1930 was actually slightly lower in the 1930s than nearly 2000 years earlier. But the word population went from 300 million to about 2 billion in that time.

Can someone help me understand this seeming discrepancy?

http://en.wikipedia.org/wiki/Black_Death

It killed off somewhere between 1/3 -1/2 BILLION people.

There's your discrepancy right there

That was in 1300's. by the 1900's, they had 600+ years to recover. And the world population was much higher in 1900 than in 100, in spite of the best nature and non-sanitation could throw at us

Coastlines and ports and such. At the height of Nazi control of the Soviet Union, much of the occupied territories were vast swaths of empty, uninhabited steppe.

Also, I would imagine as well that that were a lot of other things that killed people off over the centuries is all of those areas.

Although these answers got me thinking of other things to research to answer my own questions.

By what I can find, Germany itself, prior to WWII, seems to have had a population of about 69 million. Poland had about 39 million before the war, 24 after. France another 40 million. Even if half of both had fled the countries, and not counting the other 19 countries hitler conquered, that's still 101 million. Far more than the 75 mil the original article that cought my attention asserted.

Compared to those they conquered, the Romans may have had a more significant military and organizational advantage than the Nazis did

... the Roman weapons were far better ... The manuballista was a hand-cranked catapult that could hurl a bolt with an iron tip ... at some 50 metres per second ..; it would go through armour ... The onager .. hurled great rocks, which could demolish wooden buildings. The Roman armour was also superior; they had both chain mail ... and also heavy armour made of overlapping iron plates ... http://www.bbc.co.uk/history/ancient/romans/tech_01.shtml

And once they seized control, the Romans offered some utilities, like aqueducts and good roads -- and they enforced the peace locally. Plus, they brought some cool stuff from far away:

Roman glass dish found in grave
A rare Roman millefiori dish ... was found during excavations in Prescot Street, in Aldgate, east London ... It is made up of hundreds of translucent blue indented glass petals, bordered with white embedded in a bright red glass background ... http://news.bbc.co.uk/2/hi/uk_news/england/london/8024498.stm

The Nazis lacked some of these advantages. They had enough of a technical advantage to overrun Europe -- but for the most part, the people they conquered weren't excited about the new blessings brought by Nazi civilization: the neighborhood didn't obviously show signs of improvement, with the Nazis were strutting about; and while the "Roman peace" was real, nobody sane has ever rhapsodized about the "Nazi peace"

Moreover, WWI left a huge demographic "hole" in Europe

But even so, the world population was 6 times higher, and much of that growth was in north central europe. At least according to a Nova infographic I found.

http://www.pbs.org/wgbh/nova/earth/global-population-growth.html

Its very interesting to compare the 0 AD to the 1927 AD graphic on the interactive thingy.

while the flu pandemic was worldwide and perhaps more likely to kill the youngest and the oldest of both sexes

Healthy young adults had the best immune systems and the flu put immune systems into overdrive. Therefore, more young healthy adults died.

From wikipedia:
Tissue samples from frozen victims were used to reproduce the virus for study. This research concluded, among other things, that the virus kills through a cytokine storm (overreaction of the body's immune system), which perhaps explains its unusually severe nature and the concentrated age profile of its victims. The strong immune system reactions of young adults ravaged the body, whereas those of the weaker immune systems of children and middle-aged adults resulted in fewer deaths.<10>

What you say is, in fact, a common claim

Obviously, there are very interesting questions here

flu waves but couldn't (easily) find them.

http://www.scottmanning.com/content/year-by-year-world-population-estimates/

You look at the population of any area from the Roman Empire to 1930 such as Italy, Austria, Germany and there is simply no comparable population and the estimates of 100AD are highly questionable. Eevn Germany itself... what big cities were in Germany back during Roman times. Was there a Berlin or Munich or Hamburg in Roman times other than as small villages whereas the German population now is 80,000,000. 1930? Probably way less as they killed themselves off during WW1, but it was still probably about 50-60 million depending on where you moved the borders around after the Treaty of Versailles.
The Germans never conquered Britain, Spain, etc but they conquered the Netherlands, Norway, etc. Then again, the Romans "sort of" conquered Britain but not Norway, the Netherlands.

Perhaps they are not counting all the conquered populations for the count on germany, for some technical reason.