I’m always slightly nervous when it comes to comparing internal and external candidates. In many ways it is like moving house. On one hand you have you have the wonderful description of a potential property and beautifully taken photos and on the other, you have your current abode, lived in and known. You can take a few visits, have a look around, you can even get a surveyor’s report, but it will never amount to the knowledge and experience you have from years lived within, learning the good the bad and the indifferent.
Of course there are ways you can be more objective about the comparison, you can run aptitude tests, profiling and be as structured in the assessment as possible. But I’m not sure you can ever completely counterbalance the opportunity of being unknown. Let’s take something like stakeholder management. An external candidate will give you examples of where they’ve been successful, how they’ve managed competing demands and ultimately you can only assume this to be true. The internal candidate may tell you the same, but you’ll also have the feedback from the stakeholders themselves.
The only way I’ve found to approach this situation is to add in the equivalent of a balancing number. On one hand assume that the external candidate will be 15-20% less good than you assess them to be. On the other add a factor for growth to the internal candidate, based on your knowledge of their current performance. Then look at the two adjusted performances and try to make a comparison based on this revised approach.
Ultimately, if an internal candidate can get within distance of the external candidate based on this assessment it feels like the right thing to do to allow them to develop and grow. It’s not the most scientific approach, I grant you, but in the absence of anything genuinely more objective, I’ll be sticking to my old school ways.