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How Low Can We Go? Problems with ZIP Code Level Analyses

How Low Can We Go? Problems with ZIP Code Level Analyses. Lance Miller, MA Andrea Rodriguez, MS San Bernardino County Department of Public Health. Presentation Overview. Problem statement Purpose San Bernardino County examples Muscoy ZIP code 92401 Conclusions Solutions.

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How Low Can We Go? Problems with ZIP Code Level Analyses

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  1. How Low Can We Go? Problems with ZIP Code Level Analyses Lance Miller, MA Andrea Rodriguez, MS San Bernardino County Department of Public Health

  2. Presentation Overview • Problem statement • Purpose • San Bernardino County examples • Muscoy • ZIP code 92401 • Conclusions • Solutions

  3. Problem Statement • Public health departments use ZIP code level analysis to identify areas where program resources are needed most • Flawed source data can lead to erroneous conclusions and inaccurately targeted public health interventions

  4. Purpose • Present two problems the San Bernardino County Public Health Department has encountered with ZIP code level analysis • Discuss possible solutions to these problems, likely faced by state and local health agencies nationwide

  5. The Muscoy Problem Where the heck is Muscoy?

  6. Muscoy, California

  7. About Muscoy • Unincorporated area • Population in 2000: 9,000 residents • Land area: 2.9 sq. miles • Demographics • Educational attainment • Unemployment • Income and poverty

  8. Lack of infrastructure Increase in violent crime Restless residents Call for community needs assessment Why Muscoy? }

  9. Muscoy Needs Assessment • Resident survey • Census data • Birth outcomes • Cause of death data 10 births 7 deaths

  10. Muscoy is within 92407

  11. What else is in 92407? • Actual city name is San Bernardino • Acceptable city names include Arrowhead Farms, Devore Heights, Muscoy, and Verdemont • Are people using “San Bernardino, 92407” when they truly reside in the area of Muscoy? • How will I investigate this???

  12. Geocoding! • Using GIS software to convert street addresses into latitude and longitude coordinates • Makes locating addresses and viewing multiple locations on a map instantly possible

  13. Geocoding… • Geocoding is a must if we want to examine births and deaths in Muscoy • Teen birth events • Smaller data set – more manageable • Data exploration

  14. Startling Results • ZIP code results: Less than 5 births to teen female residents of Muscoy • Geocoded results: 40 births to teen female residents of Muscoy • That’s well over 8 times as many births!!!

  15. Is this an isolated incident? • NO! • During presentation preparation, we discovered something similar happened before… • Routine vital stats report for county health officer led to investigation of extremely high teen birth rate in ZIP code 92401

  16. How the 92401 Study Began

  17. Routine Report Finding Note: Teen birth rate defined as number of live births to mothers aged 15-19 years per 1,000 female population aged 15-19 years. Sources: 1. California Department of Health Services, Birth Files. 2. U.S. Census Bureau, 2000 Census, Summary File 1, Table P14. Prepared by San Bernardino County Department of Public Health.

  18. Health Officer’s Question • Is 92401 high teen birth rate: • artifact of data, or • real phenomenon? • To answer: • Geocoded all births indicating 92401 residence • What zip code was each birth really in (according to mapped street address)?

  19. Where is ZIP code 92401?

  20. Where is ZIP code 92401?

  21. Birth in 92401 Birth not in 92401 Mapped teen births reported as 92401

  22. Findings • Of 43 birth certificates indicating 92401:

  23. Findings Note: Teen birth rate defined as number of live births to mothers aged 15-19 years per 1,000 female population aged 15-19 years. Sources: 1. California Department of Health Services, Birth Files. 2. U.S. Census Bureau, 2000 Census, Summary File 1, Table P14. Prepared by San Bernardino County Department of Public Health.

  24. Health Officer’s Conclusions • “Perhaps … zip codes are too small to do detailed … analyses” • “We … have used zip code data … which may have been misleading to some degree if the data at this level is really so unreliable” • “Given all these analysis problems, should we expend program resources targeted to this area?” Source: Thomas Prendergast, MD, MPH, personal correspondence with Evelyn Trevino, April 2003.

  25. Conclusions • Cannot rely on ZIP codes alone for accurate geographic analysis • Data entry error • The nature of places • In order to make valid conclusions, residence street addresses must be geocoded

  26. Solutions • Good: START GEOCODING! • Better: Birth and death events geocoded at the state level • Best: Address validated and assigned coordinates at point of entry • Essential to all: Understanding the importance of accurate data collection

  27. Our Contact Information Lance Miller, Statistical Analyst (909) 387-4880 lmiller@dph.sbcounty.gov Andrea Rodriguez, Statistical Analyst (909) 387-4869 arodriguez@dph.sbcounty.gov

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