Accurately measuring ROI in L&D is the golden egg in our industry. It's what everybody wants, but what nobody has been able to achieve. In part, that's because learning is never the only thing that contributes to performance (and what is?). That makes isolating its effects incredibly challenging.
At the same time, organizations, whether internally or externally, are always looking to prove that what they are doing works. So how do we find that golden egg without destroying the goose that laid it?