[Pewpewarrows]

Comparing conversion rates of a complete before and after revamp won't tell you anything about the effectiveness of individual components of the revamp. You'd need several A/B tests or a gradual series of changes to tell you whether labels inside or out actually made a difference overall.

[byroot]

I know it's a silly argument but: do you think Facebook have made some A/B testing for their registration form ?

Because they seems to think that the placeholder as label works well [0].

[0] https://www.facebook.com/