The process took 4 weeks. I interviewed at Mercer (New York, NY) in Nov 2007
Interview
The interview was done in 2 rounds. The first round was a personality test, basic questions to determine if you were the right fit. The second round consisted of an all day interview, with 1 case study and 2:1 interview. There was also a required evening social event at a restaurant in Midtown Manhattan. The case study was fairly straightforward, with a few graphs that needed to be used to analyze the question.