11. This is based on the 1961-1990 base period ; recent years have tended to be warmer in this area. 12. The base period with an index value of 100 was set is the week ended March 16, 1990. 13. The base period , when the indexes were set to 100, is still the week ended March 16, 1990. 14. The base period , with an index value of 100, was set in the week ended March 16, 1990. 15. The base period with an index value of 100 was set in the week ended March 16, 1990. 16. "One reason is the base period for comparison last year reached its peak in October, " he said. 17. The base period was the week ended Nov . 18, when the indexes were set at 100 . 0. 18. The exact amount of workers'benefits are based on how much they earned during a 12-month " base period ." 19. This means that the index is based on a base period on a specific base day for its calculation. 20. The trade weights are not updated monthly; as of March 2016, the base period was the average over 2011-13.
