26/11/2015 Postal Code Conversion for Data Analysis An overview of the PCCF and PCCF+ Saeeda Khan Michael Tjepkema Health Analysis Division, Statistics Canada December 1, 2015 www.statcan.gc.ca Outline 1. Postal codes • Components of a postal code • Uses of small-area data 2. Introduction to the Postal Code Conversion File (PCCF) and the Postal Code Conversion File Plus (PCCF+) 3. Single link indicator geocoding versus population- weighting 4. Why PCCF+? 5. Limitations of PCCF & PCCF+ Statistics Canada • Statistique Canada 11/26/2015 2 1
26/11/2015 1. Postal Codes Statistics Canada • Statistique Canada 11/26/2015 3 What are postal codes? • An identifier managed by Canada Post Corporation for the efficient sorting and delivery of mail. • They are not created as units for the analysis or mapping of population, business or dwelling characteristics. • However, postal codes are part of most administrative data sets and are usually the only variable available for geographic identification • Thus, they are important identifiers for geocoding Statistics Canada • Statistique Canada 11/26/2015 4 2
26/11/2015 Components of a postal code • The postal code is a six-character alphanumeric code • Postal codes are not geographic attributes • Only spatial in that mail is delivered by geographic area • Six character code ‘ANA NAN’ • First 3 – Forward Sortation Area (FSA) • Last 3 – Local Delivery Unit (LDU) Statistics Canada. Postal Codes Conversion File (PCCF), Reference Guide . Catalogue no. 92-153-G, no 02. Ottawa, ON: Statistics Canada, 2011. Statistics Canada • Statistique Canada 11/26/2015 5 What is a postal code? Province / Territory / Region First Character Newfoundland and Labrador A Nova Scotia B Prince Edward Island C ANA NAN New Brunswick E Eastern Québec G Forward Local Metropolitan Montréal H Sortation Delivery Area Unit Western Québec J Eastern Ontario K Central Ontario L if 0 then rural Metropolitan Toronto M if 1-9 then urban Southwestern Ontario N Northern Ontario P Manitoba R Saskatchewan S Alberta T British Columbia V Northwest Territories and Nunavut X Yukon Y Statistics Canada • Statistique Canada 11/26/2015 6 3
26/11/2015 Components of a postal code Statistics Canada • Statistique Canada 11/26/2015 7 Components of a postal code • Local Delivery Unit (LDU) • Letter carrier delivery to ordinary urban address • Community mailbox • Apartment building • Business building • Large firm or organisation (Foothills Medical Centre: T2N2T9; CBC: M5W 1E6) • Federal department or agency (Statistics Canada: K1A 0T6) • Mail delivery route (suburban, rural, or mobile) • General delivery and post office boxes (large or small) Statistics Canada. Postal Codes Conversion File (PCCF), Reference Guide . Catalogue no. 92-153-G, no 02. Ottawa, ON: Statistics Canada, 2011. Statistics Canada • Statistique Canada 11/26/2015 8 4
26/11/2015 Components of a postal code Haydu G. The Postal Code – Geographic classification code conversion file, a tool for social science research . Paper presented at the 1979 annual meeting of the Canadian Association of Geographers, Victoria, BC, Canada. Statistics Canada • Statistique Canada 11/26/2015 9 How can postal codes be used for analysis • Postal codes are part of most administrative data sets • PCCF, PCCF+, and related tools are now the standard • Allows for the conversion of address and postal code attributes to standard geographical codes • Used in data collection, processing, and analysis, e.g., dissemination area (DA), census tract (CT), health region (HR) • Resulting small-area geography have a variety of uses • Familiarity with the methods, strengths, and limitations will help researchers exploit the potential Statistics Canada • Statistique Canada 11/26/2015 10 5
26/11/2015 Uses of small area data • Add policy relevance by aggregating to admin areas • Health Regions, School Districts, etc… • Deal with changes over time (boundary shifts) • Assign neighbourhood socio-economic status (SES) and other confounders • Determine point-distance, road distance, travel time • Allow for studies of migration over time (longitudinal) • Help in the imputation of missing data • Obtain additional identifiers for record linkage Statistics Canada • Statistique Canada 11/26/2015 11 2. Introduction to the PCCF and PCCF+ Statistics Canada • Statistique Canada 11/26/2015 12 6
26/11/2015 What is the PCCF? • A flat file that links postal codes (active and retired) to standard geographic areas • Allows for: • Association of postal codes to standard geographic areas • Selection of statistical units by geographic areas • Provides linkages (including a single link indicator (SLI)) to block face (BF), dissemination block (DB), and dissemination area (DA) • However, some postal codes are only linked to post office locations, many serve multiple DAs, and some are non-residential (government offices, etc) Statistics Canada. Postal Codes Conversion File (PCCF), Reference Guide . Catalogue no. 92-153-G, no 02. Ottawa, ON: Statistics Canada, 2011. Statistics Canada • Statistique Canada 11/26/2015 13 What is the PCCF+? • The PCCF+ consists of: 1. SAS control program, 2. reference files primarily derived from the PCCF 3. postal code population-weight file derived from the Census of Population • Assigns geographic identifiers based on postal codes • Full diagnostic output (troublesome postal codes, precision of geocoding, etc.) • Provides residential & institutional coding separately Wilkins R, Peters PA. PCCF+ Version 5K User’s Guide: Automated geocoding based on the Statistics Canada Postal Code Conversion File . Catalogue no. 82F0086-XDB. Ottawa, ON: Statistics Canada, 2011. Statistics Canada • Statistique Canada 11/26/2015 14 7
26/11/2015 Importance of Identifying Non-residential PCs • PCCF+ is able to identify non-residential postal codes • Government Offices, e.g., Statistics Canada • Coroners Offices • Children’s Aid Societies • Hospitals in a Birth File • Tax preparers office in a Tax File • UPS Store, Mailboxes Etc , Statistics Canada • Statistique Canada 11/26/2015 15 How does the PCCF+ geocode postal codes? • Assigns geographic identifiers based on postal codes in a staged approached: 1. assigns 6-digit postal codes in rural areas to disseminations areas (DA) and dissemination blocks (DB) using population- weighted random allocation 2. assigns 6-digit postal codes with an exact match to a PCCF unique record 3. randomly assigns 6-digit postal codes with an exact match to a PCCF duplicate record 4. imputes full geography for the first 5-, first 4- and first 3- digit postal codes using census population weights 5. imputes partial geography for the first 2-digit postal codes Wilkins R, Peters PA. PCCF+ Version 5K User’s Guide: Automated geocoding based on the Statistics Canada Postal Code Conversion File . Catalogue no. 82F0086-XDB. Ottawa, ON: Statistics Canada, 2011. Statistics Canada • Statistique Canada 11/26/2015 16 8
26/11/2015 Uses of the PCCF and the PCCF+ • A 2011 literature review for publications using the PCCF and PCCF+ resulted in 622 publications • Health Sciences 463 (74%) • Social Sciences & Economics 93 (15%) • Education, data, & statistics 34 (6%) • Natural & applied sciences 12 (2%) • Other 20 (3%) • Articles appeared in 233 different journals, top two: • Canadian Medical Association Journal (23) • Canadian Journal of Public Health (19) Peller P. An analysis of the Postal Code Conversion File’s use in research . DLI research paper series, 2011. Calgary, AB: University of Calgary. Statistics Canada • Statistique Canada 11/26/2015 17 3. PCCF-SLI vs. PCCF+ Statistics Canada • Statistique Canada 11/26/2015 18 9
26/11/2015 Single-link (PCCF-SLI) vs. PCCF+ • PCCF-SLI forces each postal code to be assigned to a single dissemination area (DA) & dissemination block (DB), regardless of how large the actual service area may be • For most research purposes, the distribution of the population across the entire service area is needed • PCCF+ uses a population-weighted method of geocoding where multiple-matches are possible • As such, the distribution of respondents more accurately reflects the underlying population • “Numerator - denominator consistency” Statistics Canada • Statistique Canada 11/26/2015 19 A1A 1A1 DA 1 DA 3 60% 10% DA 2 30% PCCF (SLI) PCCF+ A1A 1A1 A1A 1A1 10 6 0 1 0 3 Of 10 records reporting this postal code, Of 10 records reporting this postal code, 6 all 10 will be assigned to DA 1 using the will be assigned to DA 1, 3 to DA2 and 1 to PCCF single link indicator (SLI) DA 3 using the PCCF+ Statistics Canada • Statistique Canada 11/26/2015 20 10
26/11/2015 Population assignment using PCCF-SLI Saskatchewan Manitoba Alberta Statistics Canada • Statistique Canada 11/26/2015 21 Population assignment using PCCF+ Saskatchewan Manitoba Alberta Statistics Canada • Statistique Canada 11/26/2015 22 11
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