Small Area Statistics

(Tiny, tricky geographies, and the people who need them)

Geography

Geography and Statistics: the ‘Where”

There’s always a ‘where’ (+ time + variables)

The importance of the where varies depending on what you’re examining

Like statistics, ‘where’ displays often spur new ‘why’ questions

Why learn about small area stats?

Small area statistics: are essential for certain types of

analyses can be challenging to find, understand

and to work with; can answer local and very specific

questions can be expensive to produce and

obtain (i.e. present access challenges)

Small Area StatisticsObjectives today - to build understanding of: The relationship between geography and

statistics The terminology and hierarchical structure of

Census geography, to understand commonly accessible smaller units

Other small geographical units important to statistical display which are important/frequently requested

How to use key Statistics Canada tools to find or generate spatial display of statistics

What are ‘small area statistics’ about?

High demand for information at the ‘lowest geographic level available’

Statistics at sub-provincial, or sub-municipality level, are critical to analyses of: health (e.g. spread of disease), housing, crime, social issues (e.g. emerging patterns of

concern or interest), emergency preparedness (analysis of this doesn’t work

at a whole-municipality level), market analysis, (why do they want my postal code

anyway?) and much, much more!

Privacy and confidentiality

Keeping the unit of analysis anonymous is a challenge with small area information (if one has good local knowledge, you can identify a person)

There are rules in place about what population counts are required in order for small area statistics to be released (e.g. income)

Expense and access

Authoring agencies, because of budget limitations, (‘priorities’) are always balancing availability of variable detail and finer levels of geography

Expense and Access

More variables? > $$$

Smaller geography? > $$$ !!

No access/distribution infrastructure in place

Simply not available or collected

Geographic display

What can a map display do that a listed table cannot? Summarize the big picture – with a picture Rapidly show PATTERNS of disparity that might have

some unexpected explanation Allow display of statistics without knowledge of coding

structure for viewers

Brief words on: why Geographic Information Systems?

Small area statistics are not easily read in tables Graphic display becomes much more important at

smaller levels GIS increasingly used as a tool for small-area

analysis and summary

John Snow’s Cholera Map

No need to label the areas: the image says enough

Geographic displays of stats always involve choices, too Simple shade of color choices imply different

meanings Ranges of statistics (‘breaks’ in the data) can be

manipulated to imply different things Statistics can be left out of maps easily; what is

missing? Source statistics may be ‘bad’

Sierra Club: Deforestation

Geographic displays of statistics are subject to metadata review Evaluation of an online map display is as required

as an evaluation of statistics via metadata review; metadata criteria also apply to maps (sources should be cited, survey specified; see yesterday’s slide)

The Census Geography Hierarchy

Organizing a national system of statistical reporting depends on a full-coverage nested geographic hierarchy; i.e. geography/GIS for StatsCan is about more than making maps

The hierarchy helps to ensure 100% coverage of the population during Census collection by organizing the country’s geography

The hierarchy also defines ‘level’ of the release of statistics

Small area statistics exist at the ‘bottom’ (yet $$) end of the hierarchy

The Statistics Canada Hierarchy

Great StatsCan Geography Tools for understanding hierarchy

Nice quick tutorial: http://geodepot.statcan.ca/Diss/Referenc

e/Tutorial/HC_tut1_e.cfm

Fantastic glossary: http://geodepot.statcan.ca/Diss/Reference/COGG/Index_e.cfm

A brief hierarchy overview

All levels of the hierarchy have definitions and corresponding codes Eg. Canada – 00; Alberta (Province) – 48

The levels and codes have defined relationships Below provinces, we have Census Divisions: eg 4801 Below provinces, Census Metropolitan Areas and Census

Subdivisions Below those, Census tracts and Dissemination Areas

(SMALL AREA STATISTICS)

Hierarchy continued

Hierarchy is defined administratively (ie political decision) and statistically (ie StatsCan’s reporting requirements)

Not everything in the hierarchy relates to every other unit (see chart); i.e. not a straight, linear hierarchy

Eg. Forward Sortation Areas “Odd” units (to StatsCan): ‘Designated Places’

Hierarchy applied to statistics

Not all statistics are available for all levels of the hierarchy; parts of the hierarchy may not exist in some places

Statistical analysis is more appropriately applied to some units than to others: eg. CMA vs CSD

Hierarchy and Small Area Statistics

What are the important small area statistics in the hierarchy?

Most commonly: Census Tracts and Dissemination Areas

Other small-area data units

What people want re: geography is often not the unit of geographic availability

Data typically compiled into statistics to meet the needs of the authoring organization

Who ELSE cares about these areas/what demands are in place for this information?

Solutions are available! (We’ll look at some)

Neighbourhoods

Frequent need for statistics at this level of geography

Census tracts vs. neighbourhoods Municipalities: purchasing profiles and sharing

agreements

Postal Codes

Frequently requested for market analysis/business applications

Represented graphically by dots in a product called the Postal Code Conversion File (PCCF)

Postal codes are regions! The PCCF allows matching of postal codes to the

best corresponding dissemination area

Roads and their attributes

“Unavailable” Statistics Canada geographic areas

Some data resellers ‘impute’ or calculate estimates of ‘missing data values’ for small area statistics

GeoSuite: Walk-Through Exercise

Click-along with Leah!

Exercise: Explore the hierarchy and statistics for your favorite geographic area using StatsCan Tools

Start here: http://geodepot.statcan.ca/Diss/Maps/Maps_e.cfm

Explore the three sources available and evaluate them for usability, metadata, and for what information they have to offer you:

What were you able to discover about your chosen area from each source?

To what level of geography were you able to reach using each source?