It was the fourth consecutive monthly rise, indicating a further strengthening in employment, the Conference Board said. The business-sponsored research group said its help-wanted index reached 145 in December, up from 144 in November, 140 in October and 136 in September but unchanged from a year earlier. The seasonally adjusted index measures the volume of classified advertising in 51 major newspapers across the nation and uses a 1967 base of 100. Help-wanted advertising volume rose in six of the nation's nine regions measured, the board said. The declines were posted in the Pacific region, down 6.3%; the Mountain region, down 4.2%, and New England, down 2.7%.