Most disease rates vary by the population age. To compare rates between two areas or two time periods, differences in the age structure of the population may introduce apparent differences in the rates. To account for differences in age structure, the rates can be adjusted by applying age-specific rates to a "standard" population.

The term "morbidity" refers to the presence of illness of any kind. Morbidity is usually measured as an incidence rate or prevalence rate of a particular disease rather than an overall morbidity rate. Some diseases like cancer and HIV/AIDS are required to be reported to public health authorities. Other diseases like influenza have no reporting requirements. For some of the non-reportable diseases, we get estimates of the rates from active surveillance programs or special research studies. See Links to Health-Related Data for links to other DSHS disease data.

You can order a copy of a birth or death certificate from the Bureau of Vital Statistics by regular mail, by overnight mail, by fax, or in-person at various locations throughout the state. See Ordering Birth or Death Certificates for details.

Population estimates are generated for current and past years based on numerous factors including births, deaths, school enrollment, voter registration, vehicle registration, and housing unit data. Population projections are generated for future years based on fertility, mortality and migration trends. The Texas Health and Human Services Enterprise exclusively uses population projections based on the 2000 to 2010 census migration scenario, also referred to as the 1.0 migration scenario.  Additionally, HHSC uses population projections for reports and presentations as opposed to population estimates.  Once released, population estimates are unlikely to change; projections for Texas, however, are updated biennially as more accurate data become available. See information at the Texas Demographic Center for details.

There are 11 public health regions but 8 regional offices. Health statistics are usually summarized for each of the 11 public health regions but some programs summarize data for the 8 administrative regions. See Texas County Numbers and Public Health Regions for details.

Texas counties have both a county number and a county FIPS code. The county number is a sequential number from 1 to 254. The county FIPS code is assigned by the US Census Bureau and consists of the state FIPS code (48) followed by a three digit number for each county. See Texas County Numbers and Public Health Regions for details.

There are numerous rural/urban classification systems available. Some have two classes (rural and urban), others have a spectrum of values representing degrees of rural character or urban influence. Some are based on counties, others on census tract or ZIP code. On these pages, "urban" is typically defined as a county within a Metropolitan Statistical Area (MSA) as delineated by the Census's Office of Management and Budget (OMB).