World War 2 occurred in the late 40's, so this is most likely why there is a dip in that age group.
Daniel arap Moi ran for office in multiparty elections in 1992 and in 1997, then 1964 to 1978. From 1964 to 1978, he served as the Vice President of Kenya. He was nicknamed ”Professor of Politics” as he served in the country of Kenya for twenty-four years
Above 500 billion years ago scientific think about Earth