The recent elections in the Philippines were the first to use precinct-level optical-scan ballots. You can watch an interesting video guide for voters (a bit over 2 minutes long).
One thing that jumped out at me is that each voter is allowed only one try; if you spoil a ballot, tough luck. This is unconscionable, especially for the first use of a new ballot format. A voter must be allowed to catch a mistake, destroy the ballot, and obtain a new one (at least once!).
This appears to be exactly the system used now in San Diego County and various other US jurisdictions (except that we’re allowed to spoil a ballot and get a fresh one). Like these jurisdictions, the Philippine ballot also has several offices being elected at once, and some offices require a vote for no more than one candidate and others allow several (up to 12 for Senate!). These multiple offices and different numbers of votes only increase the risk of voter error. All the more reason to allow voters a second chance if they catch a mistake (or if the scanning machine reports an “overvote”); in fact, at least in the US, the machine’s feedback on overvotes has been claimed as one the main advantages of precinct-level scanning.
I also wonder why the Philippines chose this system instead of the electronic machines of the sort that have recently been adopted in Brazil and India.
It would be interesting to compare invalid-ballot rates before and after the change. COMELEC reported for the 2010 Senate a number of “valid ballots counted” that was exactly identical to the number of “voters actually voted.” So 100% of ballots were error-free. (I hope readers can detect the hint of skepticism here.)
Thanks to Eduardo, one of my students, for the tip.