<Tr> <Td> Oliver S. Powell </Td> <Td> Minneapolis </Td> <Td> 000000001950 - 09 - 01 - 0000 September 1, 1950 </Td> <Td> 000000001952 - 06 - 30 - 0000 June 30, 1952 </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> William McChesney Martin </Td> <Td> New York </Td> <Td> 000000001951 - 04 - 02 - 0000 April 2, 1951 </Td> <Td> 000000001970 - 01 - 31 - 0000 January 31, 1970 </Td> <Td> 19 </Td> <Td> Chairman (1951 - 1970) </Td> </Tr> <Tr> <Td> A.L. Mills, Jr . </Td> <Td> San Francisco </Td> <Td> 000000001952 - 02 - 18 - 0000 February 18, 1952 </Td> <Td> 000000001965 - 02 - 28 - 0000 February 28, 1965 </Td> <Td> 13 </Td> <Td> </Td> </Tr> <Tr> <Td> J.L. Robertson </Td> <Td> Kansas City </Td> <Td> 000000001952 - 02 - 18 - 0000 February 18, 1952 </Td> <Td> 000000001973 - 04 - 30 - 0000 April 30, 1973 </Td> <Td> 21 </Td> <Td> </Td> </Tr>

Why are the members of the fed board of governors appointed to 14 year terms