ZIP Code Tabulation Areas For Census 2000

ZIP Code Tabulation Areas For Census 2000 State Data Center Steering Committee Meeting Andrew Flora TIGER Operations Branch Geography Division USCENSUSBUREAU Helping You Make Informed Decisions TOB June 12, 1999 ZIP Code Tabulations Areas (ZCTAs™) .... are generalized area representations of United States Postal Service ZIP Codes developed by the U.S. Census Bureau for tabulating statistical data. ZCTA™ is a trademark of the U.S. Census Bureau TOB July 19, 2001 Census 2000 ZIP Code Tabulation Areas Bay County Michigan 48658 48613 48652 48650 Saginaw Bay "4 1222 " " 48634 "3 ( 486HH 48642 48631 48611 Bay City 48706 48732 48623 48623 48604 48708 487HH 48757 48747 ZCTAs .... are distinct from other area representations of ZIP Codes because they reflect address locations and ZIP Codes collected or verified during Census 2000 field operations. TOB July 19, 2001 ZCTAs .... are distinct from statistical areas such as census tracts because they are not stable over time and they are computer delineated using addresses rather than formally delineated before the census. TOB July 19, 2001 Census 2000 Dress Rehearsal Population Density Sacramento, CA Dress Rehearsal Site Comparison of Statistical Entities Census Tracts ZIP Code Tabulation Areas (ZCTA) Population / square mile < 602 602 - 1848 1849 - 4386 4387 - 6454 > 6454 Map Prepared by TIGER Operations Branch Geography Division U.S. Bureau of the Census 1999 Comparisons Census Tracts • Locally defined • Generally stable/comparable over time • Ideally 1500 housing units • Boundaries follow features • Nest within counties/county county equivalents ZCTAs • Defined by addresses and extension algorithms • Boundaries and codes change over time • Variable size • Boundaries follow tabulation block boundaries • Cross counties and states TOB July 19, 2001 Introducing ZCTAs! • New for Census 2000 • Change in methodology and content from 1990 Census • Product and trademark of the US Census Bureau TOB July 19, 2001 ZCTA Time Line 1995 1998 1999 2000 2001 2001 Begin building Prototype Process Build ZCTAs for dress rehearsal ZCTAs go public Census 2000 ZCTA Delineation Complete Census 2000 ZCTAs Census 2000 ZCTA products TOB July 19, 2001 Requirements for Building ZCTAs • • • • • Assign a ZCTA code to all areas Follow census block boundaries Assign a single ZCTA code to each block Use address ZIP Codes from MAF Match true ZIP Codes as closely as possible TOB July 19, 2001 ZCTA Codes • Represent the majority ZIP Code of the addresses in a census block • Represent a USPS 5- or 3-digit ZIP Code • Exclude unique, single delivery point ZIP Codes for firms and organizations • Include dedicated P.O. Box ZIP Codes In rural areas TOB July 19, 2001 ZCTA Codes • 5-digit numeric ZCTA codes 22301 (land & internal water) • Generic 3-digit ZCTA codes 223XX (land & internal water) 223HH (water along margins of several land ZCTAs ) TOB July 19, 2001 ZCTA Delineation Steps • • • • • • • Update the Master Address File (MAF) Calculate ZCTA as majority ZIP Code Extend coverage to unassigned areas Interactive extension, review, & update State wide review and update Tabulation block alignment Generate products & match statistics TOB July 19, 2001 Challenges for Delineating ZCTAs • Addresses with incorrect or out-dated ZIP Codes • Blocks split between ZIP Codes • Areas with no addresses or ZIP Codes TOB July 19, 2001 ZIP Code Delivery Routes ZIP Codes follow the street network Addresses with ZIP Code A Addresses with ZIP Code B TOB July 19, 2001 ZCTAs Reflect Majority ZIP Determine majority ZIP Code of available addresses ZCTA representing ZIP Code A ZCTA representing ZIP Code B TOB July 19, 2001 P.O. Box ZIP Codes Addresses with P.O. Box ZIP Codes scattered among addresses with city style delivery Addresses with ZIP Code A Addresses with P.O. Box ZIP Code B P TOB July 19, 2001 P.O. Box ZIP Codes P.O. Box ZIP Codes in areas with city style delivery are excluded from becoming ZCTAs. ZCTA representing ZIP Code A X P.O. Box ZIP Code B is excluded P TOB July 19, 2001 P.O. Box ZIP Codes Addresses with P.O. Box ZIP Codes clustered around post office in rural delivery areas Addresses with ZIP Code A Addresses with P.O. Box ZIP Code B P TOB July 19, 2001 P.O. Box ZCTA P.O. Box ZIP Codes in rural delivery areas may become ZCTAs ZCTA representing ZIP Code A ZCTA representing P.O. Box ZIP Code B P TOB July 19, 2001 Unassigned Areas Polygon Expansion assigns ZCTAs to Unassigned polygons 12346 Sm ith 12346 Sm Ri ve r ith 12347 123XX Ri ve r 12347 123HH TOB July 19, 2001 Rural Fragments • Validate ZCTA Code in fragments • Add blocks along road network to bridge fragments • Respect natural and cultural boundaries • Fill in small enclaves and “cavities” • Leave remaining area as a generic ZCTA TOB July 19, 2001 Unassigned Areas Extending and Merging Fragments of Rural Five-Digit ZCTAs SMALLVILLE SMALLVILLE 33205 33205 33210 LITTLE FALLS 33210 LITTLE FALLS TOB July 19, 2001 Unassigned Areas Extending and Merging Fragments of Rural Five-Digit ZCTAs C ount y C ount y ls SMALLVILLE Rock y Hil ls Rock y Hil SMALLVILLE rer g iviv RR e 332XX Bend Island Bend Island Park g iviv RR e Winnd Wi di ig nn Winnd Wi di ig nn rer Bend Island 332XX Park 33205 ay 33205 M M ay Bend Island 33210 LITTLE FALLS 33210 LITTLE FALLS TOB July 19, 2001 Connecting ZCTA Fragments 784X X 78411 78411 US Hwy 45 78411 78411 784X X Blocks assigned to ZCTA by software Blocks added to ZCTA by reviewer TOB July 19, 2001 Initial ZIP Code Tabulation Areas Sacramento, CA Dress Rehearsal Area 95835 95673 95660 95838 95834 95833 95815 95821 95841 95814 95816 95818 95817 95819 95825 95864 95826 95820 95822 95824 95831 95823 95828 95829 95832 0 1 2 3 Miles Areas with no MAF addresses appear in white. 95758 ZIP Code Tabulation Areas Sacramento, CA Dress Rehearsal Area 95835 95673 95660 95838 95834 95841 95833 95815 958HH 95814 95816 95819 95821 95825 95864 95818 95817 95820 95826 95822 95824 95831 95828 95829 95832 95823 0 1 2 3 Miles 95758 Initial ZIP Code Tabulation Areas Menominee, WI Dress Rehearsal Area 54150 54174 54135 0 3 6 Miles 54124 Areas with no MAF addresses appear in white. ZIP Code Tabulation Areas Menominee, WI Dress Rehearsal Area 541 54174 54150 54135 0 3 6 Miles 541HH 54124 Census 2000 ZCTA Statistics • 5-digit Numeric ZCTAs • Water ZCTAs (HH suffix) • Generic (XX suffix) • Total 32,038 809 331 33,178 TOB July 19, 2001 ZCTAs by ZIP Code Type • • • • • General use ("non-unique") 28,785 Dedicated P.O. Box 3,245 Unique (universities) 5 Discontinued (no deliveries) 3 Total 32,038 TOB July 19, 2001 ZCTA Maintenance • Monitor ZIP Code changes from USPS sources (ZIPMOVE file) • Monitor changes in summary statistics TOB July 19, 2001 ZCTA Summary Statistics • Create new MAF extract with - Latest ZIP Codes - New addresses • Match addresses and ZIP Codes to ZCTA assignments block by block • Identify negative changes in match rates TOB July 19, 2001 Products • • • • • Census 2000 TIGER/Line American FactFinder Cartographic Boundary Files ZCTA reference maps Summary Files 1 - 4 TOB July 19, 2001