I applied online. I interviewed at Mercer (New York, NY) in Nov 2019
Interview
Pleasant. Serious, but also light-hearted. Definitely centered around fit along with skill and experience. Interviews were not too long, but definitely interested in getting to know you. The questions themselves are not difficult, but you have to show knowledge in your specific area.
Interview questions [1]
Question 1
How proficient do you consider yourself with Excel?
The process was all behavioral/fit questions. Not bad, 2 interviews asking about resume/experience. A lot of time to ask questions and get a good feel for the firm. The interviews were also with a few Mercer colleagues at a time.
I applied online. The process took 2 weeks. I interviewed at Mercer (Chicago, IL) in Oct 2018
Interview
I had to do a HireVue video interview and then a Superday in their office where I was interviewed by 4 employees and had to complete a powerpoint/excel test. I also went out to lunch with some of the employees after.