The public health department of a developing country performs an epidemiologic study to assess the nationwide incidence of upper respiratory infections among children. The data show a high rate of childhood bacterial pharyngitis. Current practice guidelines indicate that a rapid test should be performed in children to identify the presence of bacterial antigens. If this test is negative, a throat culture, the gold standard for definitive diagnosis, is then performed. To offset cost and avoid losing patients to follow-up, the department is considering recommending the empiric use of penicillin for the treatment of suspected bacterial pharyngitis. Which of the following would be expected to decrease after long-term implementation of this guideline?