Two recent studies estimated how much oil was spilled in the Gulf of Mexico this summer. One came in at 185 million gallons, one at 172 million - not terribly far apart. So let's go with 180 million gallons.

"Social math" comes into play in terms of how to express a quantity like 180 million gallons (the math part) so that it has context and meaning (the social part). 

How much is 180 million gallons? We can show the same number differently, like 180,000,000 gallons - does that seem bigger? Or with more specificity, such as 179,998,780 gallons (except in this example we don't really have that degree of precision).

But to give context, we need to provide references that people already understand - this is the essence of social math and the part that transforms data into a persuasive story.

A short example: The 180 million gallons that spilled would fill 9,270 swimming pools with oil.

A longer example: The 180 million gallons that spilled could have produced about 90 million gallons of gasoline (plus a lot of other products), which would fuel driving over 1.8 billion miles, or 600,000 trips across the U.S.  Put another way, that's enough gas for every single licensed driver in the U.S. to drive about nine months of a year!

You could easily build a whole story - ones that people can easily visualize - around either of these examples.

How can you use social math in your marketing?

I believe this British Petroleum ad ran in The Economist in 1999:

And they are. Tragically ironic, isn't it? Careful of what you promise. More than your brand is at stake.