Percentage of Votes Cast
Date: 06/03/2003 at 12:20:40 From: Mary Pugh Subject: Using percentage changes on percents If you have two percentages, say 25% and 50%, can you do a percent change between the two? I don't think it is valid. It is mathematically possible to do the math, but the outcome seems bogus to me.
Date: 06/03/2003 at 14:38:31 From: Doctor Ian Subject: Re: Using percentage changes on percents Hi Mary, Suppose that in 1980, the Revisionist Party received 1% of all votes cast, while in 2000 it received 2% of all the votes cast. In which election did it receive more votes? It's not possible to say, without knowing the total number of votes. Suppose 60 million votes were cast in 1980, while only 20 million were cast in 2000. Of course, 1% of 60 million is larger than 2% of 20 million, so the party actually got more votes when it captured a lower percentage of the total vote. In fact, the percentage change in votes received would be (2% of 20 million) - (1% of 60 million) --------------------------------------- * 100 (1% of 60 million) 4/10 - 6/10 = ----------- * 100 6/10 = -33.3% However, if you're writing press releases for the party, you'd want to present things in the best possible light, so you'd focus on the change in percentage of the vote, and say that there was a 100% increase in the percentage of the votes captured by the party (i.e., our share of the vote was twice as high in 2000 as it was in 1980). Both ways of looking at it are pefectly valid. Even though the second interpretation seems kind of sneaky and underhanded, in a sense it's the more interesting one, since the in order to win an election, you don't have to attain a minimum number of votes. You just have to get a majority of the votes cast. Does this help? - Doctor Ian, The Math Forum http://mathforum.org/dr.math/
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