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Hmm.. is that statistic calculated for each individual or for the entire population. The changes are to hit are very low in either case, but there is still a large difference mathematically.

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Let's try to get an order of the probability... Let's say the parts land on earth with an an angle of more than 45 degrees. I'd take 1 sqm for each human, understanding the angle would reduce that number. Which makes around 10000 sqkm, counted generously. The earth total surface is around 510 millions sqkm. So that's one in 51000 chances for any human to be hit (calculated high). So quite makes sense that no one was impacted yet, but this seems not impossible as well - of course depending on how many satellites impact earth each year. Not counting that people are often in buildings, but one impact could kill more than 1, etc. Personally, I take this number for negligeable still. It would rather be hard finding anything build by humans killing less people.

Please correct me if I'm wrong but, your calculations don't take into account the population's distribution over the surface of the earth; most importantly water masses.

The falling debris doesn't take that into account either, so the calculation is right (give or take the odd approximation).

Might be worth taking into consideration that an object will break up into multiple pieces during re-entry.

Thought the odds are still against anyone being hit by anything.

Good point! I just found the Nasa has published on this topic: http://www.nasa.gov/pdf/585584main_UARS_Status.pdf

Risk expected is one in 10000, but for every object if I understand it well. And the current one is rather 1/3200, probably because of its size.

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