highly significantp < 0.001
During the two 5-year periods 1988–1992 and 1994–1998, there was a highly significant increase (p < 0.001) in the crude incidence rates of the stage 0 cases (i.e. high-grade colonic adenomas) by 190%, an increase in stage I cases by 14.3%, in stage II cases by 12.9%, in stage III cases by 38.5%, and a decrease in stage IV cases by 11.8%.