39887.0     9    1968-02-01
  41317.0    10    1972-01-01
  41499.0    11    1972-07-01
  41683.0    12    1973-01-01
  42048.0    13    1974-01-01
  42413.0    14    1975-01-01
  42778.0    15    1976-01-01
  43144.0    16    1977-01-01
  43509.0    17    1978-01-01
  43874.0    18    1979-01-01
  44239.0    19    1980-01-01
  44786.0    20    1981-07-01
  45151.0    21    1982-07-01
  45516.0    22    1983-07-01
  46247.0    23    1985-07-01
  47161.0    24    1988-01-01
  47892.0    25    1990-01-01
  48257.0    26    1991-01-01
  48804.0    27    1992-07-01
  49169.0    28    1993-07-01
  49534.0    29    1994-07-01
  50083.0    30    1996-01-01
  50449.0    31    1997-01-01
  51179.0    32    1999-01-01
  53736.0    33    2006-01-01
  54832.0    34    2009-01-01
  56109.0    35    2012-07-01
  57204.0    36    2015-07-01
  57754.0    37    2017-07-01
  59999.0    38    2xxx-xx-xx