I don’t know anything about archery but I am fond of math, so I thought i’d take a shot at this (ba dum tsh) This is all extremely back of the napkin, so I apologize for any errors.
So according to this, a Western round involves shooting two sets of four dozen arrows, so 96 arrows. According to this, within the US alone 23.8 million adults practice archery and 20% of those do so competitively, so 4,760,000 people in the US alone shooting competitively. There are 50 competitions scheduled in the US for 2021 according to this, which we can assume is low due to the current State Of Affairs, but it doesn’t make sense to assume that every person competes in 50 competitions a year.
If we say people who shoot competitively compete in an average of two competitions a year, that’s 4,760,000 people competing in 2 competitions a year shooting 96 arrows competitively at each competition, or 913,920,000 arrows shot competitively in a year. Even assuming robin hood-ing is a one in a million shot, we’d expect 913 robin hood shots in competition per year, or about 18 robin hood shots per competition.
Even if we assume more conservatively that only half of people who shoot competitively compete in a given year and those who compete only participate in one competition on average a year, and we then assume on top of that only the top 10% of archers who shoot competitively are able to make a robin hood shot a one-in-a-million shot, that’s still 22,848,000 arrows shot by archers good enough to make a robin hood shot a one-in a million shot yearly, and with those one in a million odds, we’d expect 22 robin hood shots in competition per year, or at slightly less than half of the competitions. Even if it’s one in ten million, we’d still expect about 2 robin hood shots in competition yearly.
So the real question isn’t ‘if a robin hood arrow is a one in a million chance, how did you see one at an archery competition?’ it’s ‘if a robin hood arrow is only a one in a million chance and not rarer, how would we not see more of them at archery competitions?’