Population of Indoeuropeans

Today, worldly, we have about:

~1,4-1,8 mld population whose male part is owner of R1 haplogroup (20-25% of mankind, with R2 it will be more).
~1,1-1,2 mld people which can be called "white european descent" (15-16% of humanity)
~3,1-3,5 mld people who are speaking indoeuropean languages as natives. (~45% of all people)

This is a huge heritage of early Indoeuropeans.

But I'm curious, how many Indoeuropeans lived before the early bronze expantion 5000 y.a.?
It is possible to estimate that number? Or maybe we can be only guessing?
It was tens of thousands? Hundreds of thousands? Millions? Any guess?

5 ka, tens or hundreds of thousands, who will tell?

yamna had allready spilled all over the Pontic steppe, corded ware and bellbeaker were about to expand, Indo Europeans were allready in the Balkans
Tochars were roaming eastward, from the steppes of Kazachstan till western Mongolia
Where were Anatolians? They were still a small tribe, about to expand. In the Balkan? Around the western shores of the Black Sea? Usatovo culture? Maybe they allready had founded Troy.
Maybe other IE tribes existed, now extinct, never made it to history.

I've always wondered about this question. I think it is generally assumed that their numbers were low relative to nearby agricultural civilizations to the South, because of their nomadic way of life. Nomads as far as I know never reach a very high population number.

I read somewhere - not remember exactly the source, sorry - that IE contribution to european DNA is estimated around 50% in northern Europe, with an east/west gradient, and around average 30% in southern europeans, except sardinians who are almost pure early european neolithic farmers, genetically speaking. Is it correct? And what do they talk about, Y-DNA only or autosomal, too?

Mars said:

I read somewhere - not remember exactly the source, sorry - that IE contribution to european DNA is estimated around 50% in northern Europe, with an east/west gradient, and around average 30% in southern europeans, except sardinians who are almost pure early european neolithic farmers, genetically speaking. Is it correct? And what do they talk about, Y-DNA only or autosomal, too?

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Those are autosomal percentages. I'm not taking it to the bank until they have more ancient dna and the analysis is done by academics, hopefully the Reich Lab. I particularly think there's a lot we don't know about the route that some of the Indo-Europeans may have taken and what dna they might have picked up before they reached Europe.