The 'sharing economy' lacks a common definition

The sharing economy is a noticeable trend shaking up traditional sectors, but the phenomenon is ill-defined and empirical evidence about its impact is scarce.

"It's always more fun, to share with everyone," Jack Johnson sang in The Sharing Song, on the soundtrack of the 2006 animation film Curious George.

The singer-songwriter proposed that a ball, a sandwich, a secret, a drum stick, time, milk, and cookies, are enjoyed exponentially when shared with others.

However, the son...