Very good - "no sooner the word than......"!!
It is clear that "only" a 6 year gap between membership periods is quite common.
Interesting to see which countries have been members the most - not always ones which one might have guessed - Lebanon and Brazil as well as France, Italy and Mexico - and China nearly every year since 1991 (it only joined in 1985)!! UK and NL only 6 and 4 years respectively in a single period each.
I see, however, that it has highlighted some data issues - e.g Albania and Algeria's 1967 membership of a WHC which didn't exist!
Re 2014 - "Qatar 2" is wrong - it has occurred because it is listed both as "chair" and as a member. India and Portugal need adding to make 21 members
Re 2013 - Algeria needs adding to make 21
Re 2012 - "Mexico 2" is wrong for same reason as Qatar in 2014. Reduce to 1 to make 21.
Re 1996 - Egypt needs adding to make 21
Re 1995 - Egypt needs adding to make 21
Re 1994 - Egypt and Syria need adding to make 21
Re 1993 - There seem to be a lot of issues here!! Currently 18 it needs
a. Removing - Japan, Niger, Lebanon
b. Adding - Cub, Cyprus, Egypt, Pakistan, Syria and Tunisia
Re 1992 - currently 20 - Cuba needs adding to make 21
Re 1991 - it is full of missing and extra countries. and stands at 16. Better to start from scratch - Brazil, Bulgaria, Canada, Colombia, Cuba, France, Greece, India, Indonesia, Italy, Mexico, Oman, Pakistan, Peru, Senegal, Syrian Arab Republic, Thailand, Tunisia, United Republic of Tanzania, United States of America, Yemen !!
Re 1990 - stands at 15 - the same problem as 1991. The full list is the same as well - Brazil, Bulgaria, Canada, Colombia, Cuba, France, Greece, India, Indonesia, Italy, Mexico, Oman, Pakistan, Peru, Senegal, Syrian Arab Republic, Thailand, Tunisia, United Republic of Tanzania, United States of America, Yemen
Re 1988 - stands at 19 -needs Malawi and Tanzania adding to make 21
The earlier years need correcting too - i will do them later!!!
On the other hand, membership periods in the "early" years were a bit "strange" so it is quite correct that Algeria did a single year in 1980!
Do you hold any other "data" about countries which could be added to the spreadsheet (can then sort by these)
a. Date of "signing" the Convention
b. UNESCO Region
c. Include countries which have never been on (but have signed of course)