We still talk about Oregon's most famous ballot initiatives using their measure number—Measure 5, Measure 9, Measure 11. What happens when those numbers come around again? Do the all-time greats get their numbers retired, like hall-of-fame athletes, or will we just have to be confused? —Kenny R.
While it's amusing to imagine Measure 11's jersey hanging in the rafters of the Capitol rotunda (or rather, it would be, if Measure 11 weren't the love-child of evil and stupid), Oregon does not retire measure numbers.
In fact, all the numbers you mention have already been reused at least once. Luckily for professional malcontents such as myself, none of the also-ran measures were particularly divisive, sparing us the drudgery of pausing mid-tirade to explain which Measure 5 we're bitching about.
Things used to be even more confusing. For most of Oregon's history, there was a new Measure 1 for every election. The system you allude to, where the tally carries over from election to election up to 99 and then starts over, wasn't instituted until 1993. The following year—a good one for fascists—brought us the infamous Measures 5 and 11.
From there, measure numbers rose apace. The great Odometer of Democracy finally turned over in 2000, and the numbers began repeating. Measure 5 Jr., the little pinko, disappointed its famous predecessor by requiring background checks for gun purchases, and Measure 11 redux was a dead-boring bond issue.
Still, it seemed inevitable that one day, two major initiatives would wind up with the same number, resulting in mass confusion, failure of the power grid and the collapse of civil society. Thus, in 2002 it was decided that henceforth the numbers would continue to rise. Soon enough, we'll see the first three-digit ballot measure. Try not to panic.