The $322 billion impact investment market is grappling with a fundamental question: How does it measure how much good it has achieved?

• Global impact funds now have over $322 billion in assets under management, PitchBook data shows.
• Many of them face a similar issue: How do they measure how impactful their investments have been?
• Relevant data collection will be the key to the industry's future success, according to a panel at MWC.

Impact investing has become big business.