Alex Scacco and Bernd Beber follow up on their analysis of the Iran election data:
After we wrote our op-ed using the province-level data, we’ve now also done some preliminary tests with the county-level data. In the latter dataset, the last digits don’t appear fraudulent. Why might we find suspicious last digits at the province level, while, at the same time, Walter Mebane and Boudewijn Roukema find evidence that first and second digits are fishy at the county level?
We can only speculate about what happened behind closed doors, but here is a scenario of top-down fraud that is consistent with the patterns found in the quantitative analyses mentioned above:
As votes began coming in on Friday night, the clerics began to think they might lose. Someone in the Ministry of the Interior then fabricated the province level results. The pattern in the last digits suggests to us that some of those vote totals were made up wholesale (why bother fudging last digits? It’s an inefficient way to shift votes around).
That still left the task of making sure the numbers in the county-level spreadsheet added up to the province-level vote counts. (And we checked — the county numbers do in fact add up to the province numbers.) A province contains 12 counties on average, so it may have been necessary to shift votes in several counties per province in order to get the leading digits to line up. This could explain possibly suspicious patterns in the first or second digit. But once the leading digits match, it’s easy to get the last and second-to-last digit to match by changing just one county per province, which isn’t enough to be picked up by our tests.
An example might make this clearer. Suppose we make up vote counts for some province, but they differ from the sum of county vote counts in the Ministry’s spreadsheet. Let’s say we happened to give one candidate 124,561 more votes than he has in the spreadsheet and another candidate that many fewer votes. There are ten counties, and no more than 100,000 votes to go around in each county. So we’ll shift 30,000 votes in one county, 20,000 in another, and so on, but we have to change first and perhaps second digits in more than one county until we have a rough match with our province-level result. But to get the numbers to add up in the trailing digits, we can change just a single county.
Again, this is just speculation. But type of centralized fraud in this story is consistent with qualitative accounts suggesting proceedings were generally clean on the ground on election-day itself, and with the strange behavior of the Ministry of the Interior the following day (for example, releasing the results early).
Our digit-based tests can’t tell us whether Ahmedinejad actually won the election. Even without manipulation, he might very well still have won. But we feel reasonably confident that the province-level numbers were tampered with.