The physiological mechanisms of  alternate bearer  mechanism differs from from one fruit crop to another fruit crop. Biennial bearing in other fruit tree species is usually the result of greatly reduced flower bud formation during the year of a heavy crop. Alternate bearing intensity is affected by the kind of rootstock, for some the production in off year represents 75% of the production observed in on year, while for others this value is only of 25%  or any other proportion. Role of genetic factors in alternate bearing production was determined between different family, genus and species .Following publications provide the calculation  of alternate bearing index...

Thanks Anoop. I agree it varies with crops and even variety. Mine is table grape in subtropics, the pattern is alternate for couple of years and then irregular, again alternate..so pretty much irregular (>6 folds)... Will go through these paper first and see how the pattern tells the story.