The Math of ROI and the Budget Deficit

How can one question have two answers?

In this election season lots of candidates are talking about the deficit. And you can find two numbers circulating: $260 billion and $560 billion. The difference is obviously 'real money' according to the quote attributed to Senator Dirksen.

The argument goes something like this:

Deficit equals revenue less expenditures. So far, so good.

However revenue consists of tax collections plus borrowed funds. Since one would expect to repay a loan, or we're just robbing Peter to pay Paul, it should be accounted for in the figures.

When considering all sources of income, the deficit is $260 billion.
When considering borrowing as only a temporary source, it is $560 billion.

A similar scenario occurs in evaluating marketing programs. ROI is often portrayed as (Profit - Costs)/Costs. But profit should only be the incremental impact of the campaign since in most cases some customers would have bought anyway.

Focusing on the difference between actual and estimated sales has a long history in the syndicated market research world, it is less common in the direct marketing world. Something to work on.