DMcG I am not about to argue with you. I also have dealt with data all my working life,compiling,collating and analysing. I have yet to encounter 100% accuracy. Any internet search on the accuracy of death certificates uncovers a host of articles in the literature, none particularly flattering when it comes to a discussion of their accuracy.
According to Geriatric Medicine:
In the United States it is estimated that the rate of major errors (eg, incorrect cause of death [CoD], incorrect manner of death) found on death certificates completed at academic institutions is approximately 33% to 40%.1 Internationally, this rate at some hospitals rises as high as 80%. I find it hard to believe they would make these figures up.