Hi!
I have a question regarding a case that McKinsey seems to use repeatedly in interviews.
The interviewer asks:
"What could be the reasons why the rhino population is declining?"
A common suggested structure is:
- Lower birth rates
- Higher death rates
- Migration
The explanation is that this is the most MECE way to approach the problem.
However, I'm struggling to understand why this is considered more MECE.
My concern is that many underlying drivers seem to affect multiple buckets at the same time. For example, habitat loss, climate change, or disease could simultaneously reduce birth rates, increase mortality, and trigger migration. Because of that, the buckets don't appear to be mutually exclusive once you start identifying the actual causes.
My instinct would instead be to structure the problem based on the underlying drivers, for example:
- Human-induced factors (e.g. poaching, urbanization, pollution)
- Environmental and ecological factors (e.g. climate, predators, food availability, disease)
- Population-specific factors (e.g. age structure, genetics, fertility)
To me, these seem closer to the actual root causes that explain why the population is declining.
At the same time, I've heard the argument that a root-cause-based structure is less MECE because it is harder to ensure that all possible reasons are covered and assigned to exactly one bucket, whereas every population change must ultimately be explained by births, deaths, or migration.
This is the part I'm struggling with.
Am I missing something, or would a root-cause-based structure like mine also be considered a valid MECE approach? In a McKinsey interview, would my approach be acceptable, or is the births/deaths/migration framework generally the preferred way to structure this type of question?
