One Tiny but Common Math Error That Adds up Big

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(Photo credit: watchwithkristin)

This election year, as in election years past, you will see one glaring error repeated over and over and over again. And it’s all a matter of simple math.

This morning I had CBS on in the background and they were reporting on the numbers for and against gay marriage. They said 38% of Americans support it now, which is “10% higher than in 2004.”

I went to the story on CBS’s website and it said that support for gay marriage was at 28% in 2004.

The difference between percent and percentage points

Do the math. If support had gone up 10%, the number would now stand at around 31%, not 38%. (10% of 28 = 2.8.)

What the anchor (or the person who wrote the copy for the anchor) meant was that support had increased by 10 percentage points. Simply saying “percent” is easier, but it’s often not accurate.

Far from it, in fact, in this case. The math actually shows that support for gay marriage has increased 35%, which is a far cry from 10%. (10/28=35.7.) And, of course, it’s a pretty big difference in meaning.

It was likely just a careless error, a way to shorthand the language for viewers. But it shows how people with more nefarious purposes can easily manipulate perceptions by deliberately substituting one for the other, making gains or losses appear to be greater or less than they actually are.

So when people cite percentages, check their math. Then, of course, express your indignation worldwide via the Internet.

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