For anyone following the nailbiter U.S. Presidential election, we keep wanting to answer the question - how does the next batch of votes affect the margin between Trump and Biden?

Let me give you a quick formula to use. You can do this faster than the TV hosts!

By how much will the next batch of votes close the gap?

*Start with what we expect the Biden and Trump vote shares to be. Let's say 60% to 40%.*

*Take the difference of the vote shares, which is the voting margin. So 60% minus 40% is 20%. *

*How much the gap closes is equal to this voting margin multiplied by size of the batch. If 10,000 new votes are released, with Biden winning 60% of them, the gap will close by 20% * 10,000, which is 2,000.*

For example, in Georgia, as of this writing, Trump leads Biden by 1,800 votes.

99% of votes have come in. So 1% are outstanding. The already-counted votes total about 5 million. So uncounted votes are approximately 50,000.

If all 50,000 get released, and they favor Biden 55% to Trump 45%, the margin is 10%. Multiply that by 50,000 means the gap closes by 5,000 votes. This would make Biden the winner.

[On the other hand, if the vote shares are reversed, of course, Trump will win Georgia. We can still do the same calculation. Instead of closing the gap by 5,000 votes, the gap widens by 5,000 votes.]

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We can also turn the question around. What is the voting margin required for Biden to overcome the 1,800 margin in Georgia? Or, what is the voting margin required for Trump to overcome the 45,000 margin in Arizona?

What voting shares will be required in the remaining votes to flip the current result?

*First, divide the current gap by the remaining votes. In Arizona, this is 45,000 divided by 340K, which is 13%. *

*Now, divide that margin by two and add it to 50%. This gives us 56.5%. So if Trump wins those remaining votes by at least 56.5% to 43.5%, he would overcome the gap of 45,000 votes. *

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A couple of issues to keep in mind when interpreting these numbers.

Whether the required level of performance is possible depends on which parts of the state the remaining votes come from, whether they are mail-in ballots, etc.

If the remaining votes are released in many batches, then remember that any batch that underperforms must be compensated by a future batch that overperforms, and vice versa.

Let's continue the above example and say Arizona releases 50,000 votes in which Trump wins 55% to 45%, which is slightly lower than required. So he would need to do better in the next batches but by how much?

The new remaining vote count is 340K - 50K = 290K. The gap widens by the voting margin x the size of the batch, i.e. 10%*50,000 = 5,000. So, the new gap is 50,000 votes. Divide 50,000 by 290K gives us 17%. Divide by 2 and add to 50% gives us 58.5%. So In the remaining votes, Trump needs to win at least 58.5% to get even.

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