Relying Solely on Postal Code to Assign People/Events to Census - PowerPoint PPT Presentation

Relying Solely on Postal Code to Assign People/Events to Census Geography or Ministry Geography Health Analytics Branch Health System Information Management & Investment Division Ministry of Health and Long-Term Care 2011 APHEO Conference May 15-16, 2011

What will we cover?  Why do we need crosswalks between different geographies? How do we assign people to different geographies based  on their postal code? Limitations and considerations when using the PCCF and  PCCF+ for assigning people and events What does this mean for public health epidemiologists  when assigning people and events to small areas? 2

Why do we need crosswalks between different geographies?  Different data sources collect different geographic locators: Census data are available at, among others, CD, CSD and DA levels  Vital statistics until 2007 included municipality and postal code but from 2008 will have  only postal code Utilization data varies:  Hospital separations (DAD) and emergency room visits (NACRS) - ministry residence • code (municipality) and postal code Medical claims (OHIP) and Continuing Care Reporting System (CCRS) - postal code •  Population health data - postal codes and/or municipalities  Geographic level at which data are available may not be that needed for analysis Different data sources may have to be linked to paint a  complete picture to answer research questions or to support program planning/decision making Postal Codes → census geography and ministry geography  3

How do we assign people to different geographies based on their postal code? PCCF and Ministry Conversion Files – using Single Link Indicator (SLI)  “The Postal Code Conversion File (PCCF) is a digital file which provides a correspondence between the  Canada Post Corporation (CPC) six- character postal code and Statistics Canada’s standard geographic areas (e.g. census subdivisions, dissemination areas, dissemination block and census tract) for which census data and other statistics are produced. Through the link between postal codes and standard geographic areas, the PCCF permits the integration of data from various sources.” - Extracted from Postal Code Conversion File (PCCF) Reference Guide (July 2009 Postal codes) MOHLTC creates, on an annual basis, a series of conversion files that link postal code to ministry  geographies: residence codes (municipality), public health unit and LHIN . PCCF+ - using random allocation  “PCCF+ Version 5 consists of a SAS control program and a series of reference files derived from the  most recent Statistics Canada Postal Code Conversion File (PCCF) and 2006 postal code population weight file (WCF) .” - Extracted from PCCF + Version 5F User’s Guide (July 2009 Postal Codes)  GIS – geographic location  The latitude and longitude of the postal code, available in the PCCF, allow postal codes to be mapped spatially. With ArcGIS, or other GIS software, postal codes can be linked to other geographies based on their geographic location. 4

How are the Ministry Conversion Files Created? 2006 Census CSD MOHLTC Residence Codes (MOHLTC) (Stat Can) All CD/CSDs All Residence Codes LHIN PHU (MOHLTC) One CSD to Residence code, LHIN, PHU (MOHLTC) Postal Code to Residence Code & PHU CSD CSD (MOHLTC) Postal Code SLI CD/CSD/DA PCCF Postal Code, CSD, DA LHIN (Stat Can) (MOHLTC) Postal Residence Codes Code PHU DA DA (MOHLTC) DA to LHIN Postal Code to Correspondence File 5 LHIN (MOHLTC) (Stats Can)

Update/Release Cycles for Different Geographies and Related Products 2006 2007 2008 2009 2010 2011 2012 PC (Canada Post) CD (StatsCan) CSD (StatsCan) CT (StatsCan) DA (StatsCan) Residence Code (MOHLTC) PHU (MOHLTC) LHIN (MOHLTC) PCCF/PCCF+ (StatsCan) Conversion Files (MOHLTC) 6

What should we be aware of when using PCCF and PCCF+ to assign people to census geography and MOHLTC geography?  Objective: To demonstrate the advantages and limitations of different methods available for assigning people/events to other geographies based solely on postal code  Methods  To assess completeness of coverage and consistency of assignment in the same year , PCCF 2008, PCCF 2009 and PCCF 2010, and their related ministry conversion files were analyzed. To assess stability of assignment over time , longitudinal analyses were  conducted. • For longitudinal comparison , PCCF 2009, was used as the reference. Assignment based on PCCF 2009 was compared with that based on PCCF 2008 and PCCF 2010 . Postal codes can be retired and reborn. PCCF includes retired as well as active  records. Only active records are included in analysis conducted for this review. 7

Limitations of Postal Code Conversion Files (PCCF/PCCF+) “ PCCF contains multiple records for a postal code when the postal code straddles more than one block-face, dissemination block, or dissemination area ”. - Extracted from Postal Code Conversion File (PCCF) Reference Guide ( July 2009 Postal codes )  Over a third of all postal codes have multiple records Especially postal codes that cover multiple address ranges, rural  routes and community mailboxes  For example: Delivery via a Rural Route – e.g. K8A6W3 PCCF 2009: 39 Active Records 8

Delivery Model Type (DMT) for Active Postal Code (PCCF 2009) Number of Active Postal Codes Delivery Model Type Description PC with Multiple Records All Active PC Percent Delivery to Face-Block Address 85,849 250,620 34.3% Delivery to an Apartment Building 753 8,575 8.8% Delivery to a Business Building 605 5,146 11.8% Delivery to a Large Volume Receiver 606 3,498 17.3% Delivery via a Rural Route 464 472 98.3% General Delivery 104 156 66.7% Delivery to a Post Office Box (not a Community Mail Box) 1,644 2,572 63.9% Delivery to a Large Volume Receiver (post office box) 2,036 2,919 69.7% Delivery via a Suburban Service 29 34 85.3% Rural Postal Code (second digit of postal code is “0”) 1,078 1,125 95.8% Total 93,168 275,117 33.9% 9

Delivery via a Rural Route – e.g. K8A6W3 Address Ranges Number Delivery Mode Delivery Installation Street Name City 2621-3859 Odd RR 2 BEACHBURG RD PEMBROKE 2654-3558 Even RR 2 BEACHBURG RD PEMBROKE 400 RR 2 COON HOLLOW TRAIL PEMBROKE 131-197 Odd RR 2 FINCHLEY RD PEMBROKE 186 RR 2 FINCHLEY RD PEMBROKE 1090-1889 RR 2 GREENWOOD RD PEMBROKE 20771-21055 Odd RR 2 HIGHWAY 17 PEMBROKE 89-476 RR 2 HILA RD PEMBROKE 1138-1838 Even RR 2 INDIAN RD PEMBROKE 1209-1837 Odd RR 2 INDIAN RD PEMBROKE 111 RR 2 INDUSTRIAL PARK RD PEMBROKE 361 RR 2 JEBWOOD TRAIL PEMBROKE 610-1292 Even RR 2 MCGONEGAL RD PEMBROKE 3033-3944 RR 2 MCLAUGHLIN RD PEMBROKE 27-170 RR 2 MEATH HILL RD PEMBROKE 499-850 RR 2 STURGEON MOUNTAIN RD PEMBROKE 1018-1071 RR 2 SUTHERLAND RD PEMBROKE 1002-1459 RR 2 VALLEY VIEW PEMBROKE 2252-2700 RR 2 ZION LINE PEMBROKE RR 2 STN MAIN PEMBROKE 10 10 Extracted from Canada Post website

Delivery via a Rural Route – e.g. K8A6W3 Address Ranges 11 11

How do PCCF and PCCF+ deal with multiple records?  PCCF and Ministry Conversion Files “The single link indicator (SLI) was created to deal with postal codes with multiple records. The single link indicator identifies the geographic area with the majority of dwellings assigned to a particular postal code. Users should be aware that only a partial correspondence between the postal code and other geographic areas is achieved when using the single link indicator.” - Extracted from “ Postal Code Conversion File (PCCF) Reference Guide ” (July 2009 Postal codes)  PCCF+ “Records for most postal codes which serve more than one dissemination area – including most rural postal codes and several classes of urban postal codes – are assigned geographic codes based on a population-weighted random allocation among the possible dissemination areas and blocks.” - Extracted from “ PCCF + Version 5F User’s Guide” (July 2009 Postal Codes) 12 12

Are all units in each geographic level covered with the different assignment methods?  “Completeness of coverage” Even when all records are included, PCCF does not cover  all units at every geographic level . When the record with the SLI is used, more areas are  missed at every geographic level  With all 3 PCCFs examined, only partial coverage is achieved at CSD, CT, DA and Residence Code levels. For example with PCCF 2009: No individual or event will be assigned to 4 CTs even if all records are used; 20  CTs will be missed if only SLI records are used.  46 CSDs are not covered if all records are used and 151 CSDs will be missed when only SLI records are used 13 13

Are all units in each geographic level covered with the different assignment methods? The table below shows the number of units covered by each PCCF by geographic level . PCCF 2008 PCCF 2009 PCCF 2010 # of All SLI All SLI All SLI Geographic Level Units Records Records Records Records Records Records CD 49 49 49 49 49 49 49 CSD 585 546 435 540 429 539 434 CT 2,136 2,132 2,117 2,132 2,116 2,131 2,117 DA 19,177 18,988 16,340 18,981 16,352 18,979 16,377 Residence Code* 684 --- 442 --- 440 --- 442 PHU* 36 --- 36 --- 36 --- 36 LHIN* 14 --- 14 --- 14 --- 14 * PCCF combined with Ministry conversion files Coverage is not an issue at PHU level (all PHU have postal codes linked to them). 14 14