I get regular emails from the Barack Obama campaign, and the one that came today contains a piece of rhetoric involving numbers that annoys me. I should preface the post with a disclaimer: the gripe is not specific to the Obama campaign; if I were receiving emails from the Clinton or McCain campaigns, I’m sure I’d find the same kind of misleading rhetoric there as well.
So here’s the offending text:
In February alone, more than 94% of our donors gave in amounts of $200 or less. Meanwhile, campaign finance reports show that donations of $200 or less make up just 13% of Senator McCain’s total campaign funds, and only 26% of Senator Clinton’s.
OK, read that through, and think about what the words mean, and whether you’ve learned anything or not about how the campaigns of the respective candidates are financed.
The implication is clear: the Obama campaign gets more of its funds from small contributions than the McCain and Clinton campaigns do. But this implication is generated by a clever manipulation of words that, with a bit of thought, are seen not to support this claim at all.
Take the first sentence:
In February alone, more than 94% of our donors gave in amounts of $200 or less.
What does this mean? It means there are a certain number of donors, and that 94% of the donors gave $200 or less. We learn nothing about what percentage of the total dollar amount of campaign contributions are from donors who gave $200 or less. The distinction is important; this is not the same thing as saying that 94% of Obama’s total campaign funding comes from people who gave $200 or less.
Let me make this concrete: Say that there were 100 donors, and 94 of them gave $200. This makes the above sentence true. Now say that the remaining 4 gave 100,000 dollars each. So the total dollar amount of campaign contributions is 94*200 + 4*100,000, which comes out to $418,800.
Now we can ask what percentage of total campaign funds were from donors giving less than $200. The answer is given by dividing the amount given by those donors by the total campaign funds, which comes out to about 4.5%. So, in this made up example, the percentage of total campaign funds coming from small donors is only 4.5%, despite the fact that 94% of the donors were small donors.
Now, consider the second sentence from the offending paragraph:
Meanwhile, campaign finance reports show that donations of $200 or less make up just 13% of Senator McCain’s total campaign funds, and only 26% of Senator Clinton’s.
It should be clear at this point how meaningless and misleading this juxtaposition is; we learned nothing about what percentage of Obama’s total campaign funds came from donors giving $200 or less, and we also learned nothing about what percentage of donors to the Clinton and McCain campaigns gave $200 or less. But the text asks us to make a meaningful comparison between the percentages given in the two sentences. So the cooperative reader thinks ‘Oh, I guess this means that the Clinton and McCain campaigns are getting most of their money from big donors, while the Obama campaign is getting most of its money from small donors’. The problem is that this conclusion does not follow from the facts given. The mathematically unsophisticated or lazy reader might even come away from the email thinking that 94% of Obama’s campaign money comes from small donors, compared to the 13% for McCain and 26% for Clinton, which is definitely false.
This sort of numerical trickery makes me mad, and even though it’s completely commonplace in any kind of political rhetoric, that doesn’t make it ok. Given the degree of innumeracy in the population, I suppose it is quite effective though.
