How to measure productivity: PAR

YOUR HELP AND FEEDBACK IS NEEDED!
People Analytics will never deliver on it's promise without being able to measure individual productivity. Whilst there's no silver bullet for this, I'm proposing to spend the next 3 months of my life (and my masters thesis) researching and creating a new metric called Productivity Against Replacement (PAR), inspired by Bill James' WAR: Wins Above Replacement
My ask is simple: Please share your feedback below, on LinkedIn or reach out directly at [e-mail] if you think it perfect, awful or anywhere in between