Tips on Using Vital Statistics
This publication is a historical recording of the most requested statistics on vital events and is a source of information that can be used in further analysis. While many users of vital statistics have a good working knowledge of this subject, others may not fully understand the data limitations. This section discusses items to help the reader use this document.
Quality of the Data
Every precaution is taken to minimize errors in the raw data during its preparation and receipt. The data are from certificates of vital events; births, deaths, marriages, divorces and annulments.
Each document is edited for consistency and completeness. Queries are initiated to complete or verify information on the certificate. The department is not able to change information on certificates without certifier concurrence. Therefore, the quality of the data is often dependent on the decisions of the certifying agent.
Residence or Occurrence
All data contained in this publication are by residence except marriages and divorces.
Totals, Rates, or Ratios
Vital events can be reported as totals, rates, or ratios. Totals will suffice as long as the user knows how many times a certain event occurred and no relationship or comparison is to be made with other areas or different periods.
When different areas or periods are being studied, it may be best to use rates or ratios. Populations vary between areas or over time in the same area. It may be that variations in occurrence result from changes in the population and do not indicate a new trend in the vital event.
Rates or ratios express the occurrence of vital events in relation to a set standard. For example, the crude birth rate is expressed per 1,000 total population; the age-specific birth rate is expressed per 1,000 females in the specific age category. This comparison removes differences between sizes of the age group being compared over time and allows for analysis of changes in vital event patterns.
Small Number Limitations
There are two limitations involving small numbers. One involves a small number of occurrences for a particular vital event. The other involves rates or ratios calculated for a small population even though the number of occurrences of that event may not be considered small. Caution should be exercised concerning the use of such data. Statistical stability cannot be assured when small numbers are used in some formulas. Determination of what constitutes as a small number must be made by the individual user. Numbers smaller than 16 and populations less than 100 are generally considered unstable for use in most statistical computations.
For More Information About Vital Statistics:
- Call (515) 281-4945, or
- Use the "Contact Us" page to submit questions online.