With the hospitals overwhelmed during the early pandemic, access to emergency department visits for non-COVID related reasons was of major concern. The study by Abel et al. examines the impact of the pandemic on the incidence rate of Ob/Gyn emergency department visits in the Kaiser Permanente healthcare system in Northern California. The authors compared three time periods in 2020: pre-pandemic 1/1-3/3, early pandemic 3/4-5/19, and late pandemic 5/20-9/1.

For each of the three periods in 2020, the number of Ob-Gyn emergency department visits, and their length of follow-up, was recorded as follows:

	Obstetric visits	Gynecological visits	Length of follow-up (in person-weeks)
Pre-pandemic (1/1-3/3 in 2020)	2,774	4,111	16,329,501
Early pandemic (3/4-5/19 in 2020)	1,931	2,972	20,027,519
Late pandemic (5/20-9/1 in 2020)	3,327	6,096	27,322,420

For all subsequent questions, please show your work with proper units. We suggest you express your answers per 100,000 person-weeks for convenience.

Calculate the incidence rates of obstetric emergency department visits in each of the pandemic periods in 2020:

a. Pre-pandemic

b. Early pandemic

c. Late pandemic