Calculate average age

[FTL]

Hi,

I have a series of columns dedicated to several names, starting from column J: e.g. from J to P one name, from R to X the second one, from Z to AF the third, and so forth (i divided them with an empty column for better reading).



Each second column of each name is his/her date of birth, and the 3rd column is his/her age (years,months with datedif function) at the beginning of each year (each row on column I is for consecutive years).

Now what i want, if possible, is to calculate the average years and months of ALL names on each year on column D. That is, how to combine each 3rd column on each name to calculate their average on a different year.

e.g. : In 1968 (cell I68), 1st name was 34 years, 6 months old (L68), 2nd name was 37 years, 2 months old (T68); in 1969 (cell I69) they were one year older (lol), and so on, so how can i calculate on each row of column D the average age of all "age" cells on any given year? There are not that many names (between 10 to 40).

Thanks in advance.