I have recently been looking at births registered at Ramsey for the period 1850-1882.

I have not done a a complete comparison with the IGI, but it would seem less than 5% of the births registered for the period to 1878 are in the IGI.

The reverse comparison has not been attempted - i.e. how many pre 1878 IGI entries (christenings) were not registered.

Illegitimacies (those registrations where no father's name is given) seem to run around 6%.

In the period 1849-1878 was it normal to either Register a birth OR to have a baptism (resulting in a PR entry) but not normal to have both.