FOR THE THIRD STRAIGHT MONTH, A SURVEY OF RURAL BANKERS IN THE MIDWEST SUGGESTS THE WEAK ECONOMIC CONDITIONS ARE STRENGTHENING, IF SLOWLY.A REPORT ISSUED BY CREIGHTON UNIVERSITY SAYS THE OVERALL INDEX FOR THE RURAL MAINSTREET ECONOMYROSE TO 38.4 THIS MONTH, COMPARED WITH 37.5 IN OCTOBER AND 36.5 IN SEPTEMBER.THE NEW FIGURE IS WELL BELOW THE GROWTH-NEUTRAL SCORE OF 50 BUT FAR ABOVE THE RECORD LOW OF 16.9 SET IN FEBRUARY.Just to give you an idea...THE INDEX RUNS 0 TO 100.ORGANIZERS SAY A SCORE BELOW 50 SUGGESTS THE ECONOMY WILL CONTRACT IN THE NEXT FEW MONTHS; ABOVE 50 INDICATES THE ECONOMY WILL EXPAND.THE SURVEY COVERS Minnesota, Iowa, South Dakota, North Dakota, COLORADO, ILLINOIS, KANSAS,Missouri, MONTANA, NEBRASKA AND WYOMING.