A paper in the early year to investigate the effect of packet reordering to application throughput (esp. TCP). The conclusion is trivial but it gives some numbers:

While at small reorder rates there is little effect, at rates starting from 0.1 to 1 percent (depending on the delay), a much fast drop in application throughput takes place

Bibliographic data

   title = "The Effect of Packet Reordering in a Backbone Link on Application Throughput",
   author = "Michael Laor and Lior Gendel",
   journal = "IEEE Network",
   pages = "28--36",
   month = "Sep/Oct",
   year = "2002",