As an epidemiologist for the Colorado Department of Public Health and Environment, you have been tasked with calculating the incidence density rate of HIV among women aged 18-65 years in 2005-2015 in Denver County. Disease tracking systems in your department have provided the number of newly diagnosed cases of HIV for your target population between 2005-2015 (10 years worth of cases). What is the best data collection method to obtain the denominator? (select one best answer)

Census estimates of population of women aged 18-65 in Colorado in 2010, obtained from the Colorado State Demography Office, which you will multiply by 10.

Conduct a door-to-door survey to count the number of women aged 18-65 in Denver in 2015.

Request a list of registered voters from the Colorado Secretary of State's office and use average the number of female registered voters age 18-65 in Denver between 2005-2015 as your denominator.

It is impossible to calculate the incidence density rate because you cannot obtain the individual person time of follow-up of each woman aged 18-65 in Denver between 2005-2015.