FIGURE 1. Population adjusted secular trends for perforated and nonperforated appendicitis and negative appendectomy rates in males (A) and females (B). Nonperforated appendicitis was determined from diagnostic codes for the disease entity appendicitis. Time series analysis found a significant year-to-year correlation between residuals of nonperforated and perforated appendicitis rates in males (r = 0.55, P = 0.001) (C) but not in females (r = 0.21, P = 0.25) (D). The year-to-year changes in the residuals of the nonperforated appendicitis rates of males and females were correlated (r = 0.49, P = 0.004), as were those of negative appendectomy rates in males and females (r = 0.45, P = 0.009; data not shown).