Dear [ ],
Of course there is a rejection rate in McKinsey's Decision Round. If there weren't, the round would be eliminated altogether as there would be no Decisions to be made.
That said, the rate is much lower than the First Round rejection rate (for obvious reasons), and, in my limited experience, tends to be lower than 50%. In other words, less than half of the candidates who get invited to Decision Rounds are ultimately rejected. When I reference a 'limited experience,' I refer specifically to two smallish sample sizes:
a) my fellow MBAs who applied for and received full-time offers with McKinsey, and, b) a small smattering of Experienced Hires who recruited with McKinsey at later stages in their career.
Here are two reasons why I believe the rejection rate tends to be lower than all other stages of the recruitment process:
1) Demonstrated skill: aspiring consultants who have made it through the CV selection, the Problem Solving Test, and two First Round Case and PEI interviews clearly have the skill set to be potentially good consultants. By the Decision Round stage, the more 'normalised' distribution of talent and skill has self-consolidated into the top decile, and a greater uniformity of superior skill sets are observable across candidates.
2) Reputation of Referees: To get to the Decision Round requires two Engagement Managers/Principals endorsing your potential talent as a future consultant to McKinsey's senior leadership. And that comes with a reputational stake for them. Your First Round interviewers would not dare put someone in front of a Partner whose potential for career success they held in any doubt.
The skills to close the deal in the Decision Round (in addition to all those demonstrated in previous stages) are: likability and presentability; emotional and professional maturity; client-readiness & crisp and effective communication; and a demonstration of sound business judgement.