When you make a bad prediction, you need to be sure that you don’t lose your nerve. The best thing to do is to assess your new information, pluck up your courage, and make a brand new prediction about something else …
Megan McArdle was wrong about Iraq, but those of us who were right on every important detail (we know who we are) shouldn’t be acting all smug, and we certainly shouldn’t be making acid remarks about the credibility of the people who got it wrong, because hey, the important thing is to all learn from this experience so that we can make better decisions and predictions in future. No really, it was the antiwar side that had made up their minds before making any arguments, the antiwar side that kept changing their arguments with the prevailing winds, and the antiwar side that were the worst offenders in terms of nasty triumphalism afterwards. Me neither.
I’m not sure I recall this “let’s not argue about who killed who’s cat” stuff as being a particularly common reaction in the right wing blogosphere to massive failures in public sector projects, but there is more joy in heaven, etc, etc, etc. At the very least, presumably Megan won’t be quite as quick to start acting as a news aggregator for Lancet mortality study hacks and cranks, next time round.
So anyway, if we’re all learning from our mistakes and improving our decision making processes, then probably the best way of going forward is to take what we’ve learned about the advisability and consequences of the Iraq War as it was fought in 2003, and apply them to the new, very similar, but smaller and therefore easier problem of predicting what will be the result of the “surge” strategy of sending 20,000 more troops there now? Personally, I think it’s not going to work. How about you, Jane Galt?
 Actually I screwed up pretty badly once, in 2005, on Iraq, because I predicted that the secularists would have much more success in the elections than they actually got, and that the base of support for the insurgents was much smaller than it actually was. Looking back at the original post, it appears that my main mistake was that I read the Economist and believed it. I have adjusted my weightings accordingly.
 Sorry, can’t be more specific than that. Off the top of my head I can come up with five scenarios:
a) Al-Sadr shifts his operations to another part of Iraq, leaving a load of troops doing nothing in Sadr City as open street war flares up in Basra
b) The US troops get bogged down in urban combat until their Iraqi allies turn on them and/or a massacre of civilians happens
c) Military coup or other collapse of the Maliki government
d) Al-Sadr demonstrates his political nous once more, and calms down his operations, carrying out only enough hit-and-run attacks on US troops to keep his popularity up. Then he forms a nationalist bloc with one or more of the Sunni parties. Political collapse of the Maliki government.
e) outright Rwanda-style massacre of Sunnis and Sadrists by the Badr Brigades.
the point is that there are about a million ways in which this could go wrong, and only one way it might go right, a point that John has made on a number of occasions.