Contrary to popular opinion, it is not true that only what gets measured gets done. If it were, business, government, and society at large would come to a halt due to the damage done by metrics gamers, and for the lack of the contributions made by people who do not care whether they are measured. Deming is often quoted on this subject, as saying:

• “It is wrong to suppose that if you can’t measure it, you can’t manage it – a costly myth.” (Deming, The New Economics. p.35)
• “People with targets and jobs dependent upon meeting them will probably meet the targets – even if they have to destroy the enterprise to do it.” It is cited on Brainy Quotes, but without a source, and it may be apocryphal.

As he showed in his “red bead experiments,” his primary concern was about people being rewarded or punished based on random fluctuations in metrics that have nothing to do with their talents or efforts, but there are even more fundamental challenges in an area like people development.

You can measure how much dirt you have shoveled by weighing it, but developing people is different. There is not even a single direction. Some individuals are “hedgehogs,” who know one big thing like heat treatment, while others are “foxes,” who know many things like all the technical and human moving parts of a production line.

There is no metric– or even set of metrics — that can reasonably summarize people development, but it is nonetheless tangible and observable.