Below is the letter that I wrote to CNBC World:
For years I have noticed that your reporters (both CNBC and CNBC World) have problems with their math. Today at around 3:15am, I heard Claudia from Milan reporting on your network that a certain stock was "up by six percentage points". Since stocks are measured in points, it is mathematically incorrect to say that a stock is up by a certain number of "percentage points". Stocks aren't measured in percentage points. A stock increases by a unitless percent. It makes no more sense to say that a stock is "up by six percentage points" than it does to say that a stock is "up by six oranges". The only things that increase by percentage points are those that are actually measured in percentage points. If Bernanke were to raise the Fed Funds rate from 0.25% to 0.50% that would be an increase of 0.25 percentage points but since the rate doubled, it actually increased by 100%. Clearly percentage points and percents are two completely different things. So this is why is hurts my ears to hear your reporters use "percentage point" when they should be saying "percent", perhaps in an unconscious effort to sound more official. But what they are saying is mathematically nonsensical. I expect better from a financial network.
Best regards,
Mark Kronenberg
Founder, Math 1-2-3®, Inc.
Specialists in Math Tutoring & Test Prep
888-math123
www.math123.com
