Maybe you thought you’d left math behind forever once you landed a job in journalism. But for the numerically handicapped, some practical advice.

Explaining percentage of change is a standard of news reporting. People want to know not only how much, in numbers, something increased or decreased, but also the percentage of that increase or decrease.

The list of increase/decrease is almost endless, and you have to calculate it. Don’t fret: calculating percentage of change is easy. The steps are all simple:

List. Subtract. Divide. Multiply.

In calculating percentage of change (whether an increase or a decrease) you are concerned with the difference between two numbers and how much of the first number added to or subtracted from the first number will produce the second number.

It only sounds complicated. The key is that the percentage of change is based upon the first number only. Remember that. Remember the steps: List. Subtract. Divide. Multiply.

Calculate percentage of change this way: List the numbers in rank order, old number first:

budget -- 1996 -- 1997

$1,738,953 -- $2,033,864

Subtract the smaller from the larger: 

2,033,864 minus 1,738,953 equals 294,911.

Divide by the first number: 294,911 divided by 1,738,953 equals 0.1695911.

Multiply by 100: 0.1695911 times 100 equals 16.95911 or 17 percent.

Because the second number is larger, the change is an increase, of 17 percent.

If the numbers are reversed, follow the same procedure.

List the numbers in rank order, old number first:

budget -- 1996 -- 1997

$2,033,864 -- $1,738,953

Subtract the smaller from the larger:

2,033,864 minus 1,738,953 equals 294,911

Divide by the first number:

294,911 divided by 2,033,864 equals 0.1450003

Multiply by 100, for 14,50003 or 15 percent. 

Because the second number is smaller, the change is a decrease.

Remember, the percentage of change is based upon the first number and the change from the first number. Sometimes you can look at the two numbers and recognize the percentage of change. If the first number is 2 and the second is 3, the difference, 1, is an increase of 50 percent because 1 is half of 2, which, added to 2 equals 3, the second number.

If the first number is 3 and the second number is 2, the difference, 1, is a decrease of 33 percent because 1 is one third of 3, which, subtracted from the first number equals 2, the second number.

They’re different:

Percentage points are different from percentage of change and from percentages, and they need only a definition to make them become clear.

A percentage point is the number that a percentage is increased or decreased. Remember, you are dealing with percentages, not whole numbers.

If a bank increases the interest rate from 12 percent to 15 percent, the percentage of change is an increase of 25 percent, but the interest increased by 3 percentage points, from 12 percent to 15 percent.

If the bank decreases the interest rate from 15 percent to 12 percent, the percentage of change is 20 percent, but the number of percentage points of change remains at 3, from 15 percent to 12 percent. 

And we all go refinance our debt.

(ALSO, check out the Philadelphia Inquirer's  Essential Numbers  site)