All data has been derived from the transcriptions in the IGI derived from the official 1911 transcription - thus it is a transcription of a transcription of an earlier transcription !
Based on various Church, Civil and, post 1821, Decennial Census data
The register starts from 1666. The Register notes following 1704 "This
year the Revd Mr Samuel Watleworth came to Kk Andrews..."
On the marriage register is written "Note, There were no Marriages writ in the Church Registry from 1685 to 1704, during Parson Xtian's & Mr Curghy's time in Kk Andrews till Mr Archdeacon Watleworth came to this Parish."
Unfortuneately the IGI entries for Andreas, Marown, Michael, Lezayre and in part St Marks look as though complete years or decades were re-transcribed and entered into the IGI under various batch numbers in the 722xxxx and 723xxxx series which appear as Patron submitted records prior to 1991 (call these the 'new' entries). When you fit these up against the remaining entries claiming to be from Parish Register transcriptions (call these the 'old' entries) it is obvious that those old entries which matched the new entry were deleted and thus appear with the 723xxxx batch, those that did not match (eg changes in transcription) remained thus giving the highly useful result that most of those that claim to be parish records are wrong transcriptions whereas the possibly more accurate ones are tagged as the generally unreliable (and at times totally spurious) patron submitted variety. The above graph is a partial reconciliation - I suspect the gaps from 1725 to 1780 are caused by missing records (I do not have easy access to the PR's at present to check).
St Jude's is a chapel-of-ease within Andreas, its baptismal register starts 1846, most, but not all, of its entries appear also in the Andreas baptismal register and are not shown above.
See page on Andreas Marriages 1655-1685. The curve is based on original parish register until 1757 and IGI data thereafter (still to be checked) .
The peaks are 1675-6 and 1725, in both cases over 10% of the parish died in one year - see epidemics.
R.A. Houston The Population History of Britain and Ireland 1500-1750, Macmillan Education Studies in Economic and Social History (ISBN 0-333-56564-9) 1992