How many professional piano tuners are there in Melbourne?

This question was asked at an interview for an FX-options trader position at a Big Four Australian bank.

The question in full

We want you to tell us how many professional piano tuners there are in Melbourne, and walk us through your logic for coming to your final answer.

The candidate’s response

• 4m people in Melbourne
• Average household = approximately three people, therefore 1.3m households
• Households are divided into 1/3 wealthy, 1/3 middle, 1/3 lower-income brackets
• Wealthy more likely to afford a piano. Estimate 45% of wealthy households have a piano, middle 30%, lower 15%: provides average 30% of households have a piano = roughly 400,000 pianos in Melbourne
• Piano needs to be tuned every three years, therefore 130,000 pianos need tuning each year in Melbourne
• Tuning takes 1.5 hours, therefore 200,000 hours of Piano tuning work in Melbourne
• Full-time piano tuner works 40 hours a week, therefore 40 x 52 = 2000 hours worked per year after annual leave
• 200,000/2,000 = 100 piano tuners required to service Melbourne area

Then they asked me how I would go about confirming my logic, and my response was "via the Yellow Pages".

The answer

They then pulled out the Yellow Pages and told me there were actually about 150 piano tuners in Melbourne.

Did the candidate get the job?

The candidate ended up taking a different role that he/she was applying for simultaneously, so he/she had exited the interview process before an offer/rejection was made.