@techreport{NBERw13800,
 title = "None",
 author = "None",
 institution = "National Bureau of Economic Research",
 type = "Working Paper",
 series = "Working Paper Series",
 number = "13800",
 year = "2008",
 month = "February",
 URL = "http://www.nber.org/papers/w13800",
 abstract = {This paper has been withdrawn.},
}