0 0 SMALLER THAN ANY VALUE IN THE 30-YEAR PERIOD
1 1 IN THE FIRST QUINTILE
2 2 IN THE SECOND QUINTILE
3 3 IN THE THIRD QUINTILE
4 4 IN THE FOURTH QUINTILE
5 5 IN THE FIFTH QUINTILE
6 6 GREATER THAN ANY VALUE IN THE 30-YEAR PERIOD
15 15 MISSING VALUE
