I fell off the turnip truck a long, long time ago (Part II)

Previously, off the end of the truck… this.

Here is a description of someone’s history of giving: “Your charitable donations have gone up 100% compared with 10 years ago.”

Here is another description of someone’s history of giving: “Your charitable donations have gone down by 50% compared with 10 years ago.”

If you were a university fund-raising officer, which of these ‘someone’s would you rather target for that alumni dinner with the Dean?

On the surface of it, it seems pretty clear cut.

But it is not.

And every day (every day), the thinking person needs to filter the motivation of every author who presents or posts an idea. And particularly when they are quoting numbers, because we automatically, subconsciously, tend to regard numbers as clear and objective evidence without the intrinsic ambiguity that natural language can present.

But it is not that clear or objective. Keep  my two statements about those charitable donations in mind.

Ten years ago, when you were earning $50,000 a year, you made $5000 in charitable donations, which was 10% of your income. This year, you donated $10,000 from your $200,000 earnings, which was 5% of your income.

Turns out there are not two ‘someone’s in my original scenarios, and those seemingly contradictory statements are simultaneously true.

$5000 ten years ago; $10,000 this year; this means:

“Your charitable donations have gone up 100% compared with 10 years ago.”

10% of your salary ten years ago; 5% of your salary this year; this means:

“Your charitable donations have gone down by 50% compared with 10 years ago.”

Relative measurements (high, low, more, less, warm, cool…) all require additional absolute information (the point of reference) to understand them. Always think about that when people talk in percentage change.

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