1. VITAL STATISTICS
A branch of statistics that deals with the changes and most basic events of human populations: e.g., natality (birth); mortality (death); morbidity (illness and disease); injuries; marriage . . .
Vital statistics are indispensable in studying social and health trends, and making important legislative, commercial (marketing) and health decisions
Statistics are gathered from census and registrars’ reports, physicians’ records, medical examiners’/coroners’ records, funeral directors, and a variety of other health professionals

2. VITAL STATISTICS
In the United States, national statistics are compiled and published by the Public Health Service of the Department of Health and Human Services
The most important element in vital statistics is the rate, which customarily represents the average of births or deaths (incidents) for a unit of 10 during a given period of time (usually a year). General rates are called crude rates; when subdivided into sex, race, age, occupation, locality, etc., these are known as specific (refined) rates

3. RATES: DENOMINATORS AND NUMERATORS
Rates or ratios are used to measure most health problems
They consist of numerators and denominators: a count of events divided by the number of possible events
Numerators and denominators used in public health statistics are of three types:
Survival data (births, deaths, and a count of the population
Health and socioeconomic status data
Data based on health resources and utilization

4. THE DENOMINATORS
The most important information on which activities in public health must be predicated is a count of the population to bee served
The decennial census is an important and the most widely used information as the denominator
May include intercensal estimates, based on projects or sample surveys
Other sources of information may also be used, depending on the phenomenon of interest; for example --
School enrollment records
Employer records of numbers of workers

5. THE DENOMINATOR
Airline carriers for numbers of passengers carried during a given time
Numerator data stem from administrative registration and reporting procedures
Most significant of activities relate to the vital events of birth, mortality (death), and morbidity (disease, illness, and injury

6. INCIDENCE AND PREVALENCE
Incidence Rate
Number of new events occurring during a reporting period (such as cases of measles), divided by the population at risk of the events
Incidence may be calculated for a week, a month, a year, or any period that is helpful in explaining the phenomenon
Prevalence Rate
Number of cases existing at a particular time, divided by the population at risk of the event
Prevalence is typically referred to as point prevalence, since it calculated at a particular point in time

7. In both incidence and prevalence rates, a constant has to be selected, based on the frequency of the event
E.g., for very rare diseases or conditions, such as leukemia, the constant may be 100,000, whereas it might be 1,000 or 100 for more common conditions, such as live births