Dear all,
I just want inform everybody about an interesting (and simple) mathematical calculation I have done based upon the famous Pareto principle, which makes it possible to estimate how the 21 million bitcoins approximately will be distributed over the population in a future world dominated by bitcoin (i.e. everybody using it, which remains to be seen).
Here are the results of my calculation:
Wealth level 0: On average 0.0007 bitcoins (held by 6 billion people = the average person)
Wealth level 1: On average 0.0028 bitcoins (held by 1.2 billion people)
Wealth level 2: On average 0.011 bitcoins (held by 240 million people)
Wealth level 3: On average 0.045 bitcoins (held by 48 million people)
Wealth level 4: On average 0.18 bitcoins (held by 9.6 million people)
Wealth level 5: On average 0.72 bitcoins (held by 1.92 million people)
Wealth level 6: On average 2.9 bitcoins (held by 384 000 people)
Wealth level 7: On average 11 bitcoins (held by 76 800 people)
Wealth level 8: On average 46 bitcoins (held by 15 360 people)
Wealth level 9: On average 184 bitcoins (held by 3 072 people)
Wealth level 10: On average 734 bitcoins (held by 614 people)
Wealth level 10 turns out to approximately correspond to being a dollar billionaire in today's money!
If you want to know the details of how I calculated these results, please read my article at:
https://steemit.com/bitcoin/@mandrake7/calculating-the-number-of-bitcoins-required-to-reach-a-given-wealth-level-in-a-future-world-dominated-by-bitcoinand give me an upvote if you liked it

Please do not see this post as investment advice, you are yourself responsible for your investment decisions.
Do you have any details on what the wealth levels mean? You mentioned wealth level 10 would be a dollar billionaire, what about the other wealth levels? Without that it is pretty hard to consider. It would also be interesting to consider population growth, by the time 6bn people are using bitcoin the population will probably be 10bn+