Table:
text: Municipal Borough of East Retford
Borough Council
Borough Council
Year_ Conservative_councillors Labour_councillors Independent_councillors Liberal_councillors_
1947 3 2 18 1
1951 5 2 17 0
1952 3 3 18 0
1953 4 3 17 0
1954 3 4 17 0
1955 2 5 17 0
1956 2 6 16 0
1957 2 5 17 0
1958 2 6 16 0
1960 2 5 16 1
1961 2 5 15 2
1963 2 6 12 4
1964 3 6 11 4
1965 4 5 11 3
1966 9 4 6 5
1967 9 4 9 2
1972 10 10 3 1

text: Municipal Borough of East Retford
Borough Council
Borough Council
Year_ Conservative_councillors Labour_councillors Independent_councillors Liberal_councillors_
1947 3 2 18 1
1951 5 2 17 0
1952 3 3 18 0
1953 4 3 17 0
1954 3 4 17 0
1955 2 5 17 0
1956 2 6 16 0
1957 2 5 17 0
1958 2 6 16 0
1960 2 5 16 1
1961 2 5 15 2
1963 2 6 12 4
1964 3 6 11 4
1965 4 5 11 3
1966 9 4 6 5
1967 9 4 9 2
1972 10 10 3 1

Question: In how many years has the borough of East Retford not had a Liberal councillor?

Question: Why haven't Liberal councilors served in East Retford Borough for years?