Several years ago, when the US government had finally signed a deal to avoid the fiscal cliff, I was quickly confused about what the deal was. On the airwaves, I had heard that part of the deal would be a 2% increase in payroll taxes, yet in print, I had read that there was to be a 2 *percentage point* increase.

There can be a big difference between 2% and 2 percentage points.

**Proportion and Precision**

*Percent* is a specific portion of a given value, with the whole of the value being 100%. For example, if I invited 50 people to a party, and the portion who actually came is 60%, then 30 people attended my party:

50 x 0.60 = 30

A *percentage* is an unspecified portion of a given value. Using the example above, I could say *“*a percentage of the people I invited actually came to the party.” Although rare, a numerical value can be listed in relation to *percentage*, but the number comes after *percentage*, as the object of a preposition, rather than as a modifier of *percentage*:

She hit 22 homers on the season, with a slugging percentage of .968, and posted a record of 20-3 on the mound.

San Francisco Chronicle

Pretty straightforward, right? Language users get *percent* and *percentage *right without thinking too hard about it.

But here’s what we often miss: *percentage point* is, as Mark Allen once wrote in an article titled *Become a Numbers Person*, “a point along a 100-point scale related to the whole scale rather than related to a number being compared.”

We’re talking about two different measurements here. A percent change is a proportional change that does not, as the *AMA Manual of Style* points, “indicate the actual beginning or ending values or the magnitude of the change.” A percentage point change is a mathematical, or numerical, change, which does give you an idea of the magnitude of the change.

**$84 vs. $2,00**0

Let’s go back to our original example. The US payroll tax rate in 2012 was 4.2%. That is, 4.2% of your income went to Uncle Sam. For the sake of simplicity, let’s say you earned $100,000 in 2012. Of that amount, you paid 4.2%, or $4,200, in payroll taxes:

100,000 x 0.042 = $4,200

If the payroll tax were going to be 2% higher in 2013, that would mean the rate would be increasing a portion of the starting rate. That is, we would be paying 2% of 4.2% plus the original 4.2%, or 4.284%.

Again for simplicity, let’s say your salary will stay the same in 2013. This year, you’ll pay $4,284 instead of $4,200 ($100,000 x 4.284%). That’s not a bad increase.

But that’s not what’s happening now. Look closely, and you’ll see that the current payroll tax rate is 6.2%—a percentage point increase. What will you pay out in payroll taxes in that case?

$100,000 x 0.062 = $6,200

Numerically speaking, a $2,000 increase is substantially different from an $84 increase!

**Practical Usage**

Here’s the big question: is the usage distinction between *percent* and *percentage point* recognized outside of industry texts, such as financial reports and medical studies? In other words, does a general audience understand what is meant when they hear that there will be a 2% payroll tax increase?

It’s not unusual for industry definitions to become less precise and more generic when they are co-opted by a general audience. That audience doesn’t know all the ins and outs, just the summary information. And though it drives those who know the difference crazy, that’s just the way life works.

In this case, those who don’t know the distinction between *percent* and *percentage point* seem to be making a leap in logic and coming up with the right answer. At least according to the reports I’ve heard. Perhaps the inclusion of the new and old rates, 4.2% and 6.2%, helps in that leap.

Printed news stories about the payroll tax increase are more precise, however, using *percentage points*. I’ve only *heard* references to a percent increase, not read it. So at least in print, we are opting to be more precise. It makes sense. In print we have the time to do the math and think about the logic. Plus, readers can’t ask for clarification and get it quickly. Without the precision in print, we risk a potentially huge misunderstanding.

But even in formal speech, we should be careful. Again, listeners might not have an opportunity to ask for clarification. It’s important for writers and speakers to not only know their facts but also communicate them in a way that eliminates confusion or misunderstanding as much as possible.

Numbers can be confusing, particularly when you don’t know all the details behind them. For clarity’s sake, use the precise meanings of *percent* and *percentage point* to get your message across.

*A version of this article originally published on January 10, 2013, on *Virtual Thesaurus.