AP® Human Geography review sheet from Aim for Five (aimforfive.com/geo/units/6/6-9)
Unit 6 · Topic 6.9
6.9 Urban Data
Geographers study cities with quantitative data, like census counts and survey results, and qualitative data, like interviews, field observations and residents' stories. Each kind reveals different things, so combining them gives a fuller, more accurate picture of how neighborhoods are changing.
Key terms
- quantitative data
- qualitative data
- census
- survey
- field observation
Quantitative data
Quantitative data are numbers that can be counted and measured. For U.S. cities, the main sources are:
- The decennial census: a count of every resident every 10 years, most recently in 2020, with basic facts like age, sex, race and ethnicity, and housing.
- The American Community Survey (ACS): a yearly survey of a sample of households that estimates income, education, commuting, rent, languages spoken and more. Because it's a sample, each estimate comes with a margin of error.
- Other sources: building permits, property values, school enrollment, crime reports and business counts.
| Scale | What it is | Useful for |
|---|---|---|
| Census block | Often a single city block | Very local population counts |
| Census tract | A small area, usually about 1,200 to 8,000 people | Comparing neighborhoods over time |
| County or city | A local government area | Regional comparisons |
| Metropolitan area | A core city plus the surrounding counties linked by commuting | Comparing whole urban regions |
Qualitative data
Qualitative data are descriptions, not numbers. They include interviews, oral histories, field observations, photographs, mental maps (sketches of how people see their own area) and residents' stories. They explain why things are happening and what they mean to people. A census table might show rents rising in a neighborhood; interviews can show that longtime residents feel pushed out, or that new businesses don't serve them.
Using data carefully
- Scale changes the picture. A city's average income can hide very rich and very poor neighborhoods. Looking at tracts instead of the whole city can reveal segregation or gentrification that the citywide number hides.
- Boundaries matter. The same data grouped into different areas can show different patterns. For example, the UN's 2025 switch to one method for drawing city limits changed the world's largest-city ranking (6.2).
- Definitions change over time. The census has changed how it asks about race and ethnicity, so comparisons across decades need care.
- Samples have error. ACS estimates for small areas can be uncertain, especially for small groups.
- Qualitative data can be shaped by who is interviewed and who isn't, so researchers try to hear from different groups.
Why combine the two
The strongest urban studies use both. Numbers show the size and speed of change, like how fast rents rose or how a tract's population shifted. Qualitative work explains causes and effects on people's lives. Planners use both when deciding where to put a bus line, a clinic or affordable housing.
Worked examples
Try each one yourself first, then open the solution.
- Example 1
Reading data for a neighborhood change
A hypothetical census tract changed from 2010 to 2020 as follows: median household income rose from $38,000 to $71,000, median rent rose from $850 to $1,600 a month, and the share of residents with a bachelor's degree rose from 18% to 52%. Total population barely changed. Describe what these data suggest and explain one limitation of using them alone.
Show the solutionHide the solution
- Step 1: Describe the pattern: income, rent and education all rose sharply while population stayed about the same.
- Step 2: Interpret it: a stable population with very different characteristics suggests many residents were replaced by wealthier, more educated newcomers, a sign of gentrification.
- Step 3: Name a limitation: the numbers can't show whether longtime residents were displaced or simply got raises, or how residents feel about the change.
- Step 4: Suggest a fix: interviews or tracking where former residents moved would fill that gap.
Answer: Model answer: The sharp rise in income, rent and college degrees with little population change suggests gentrification: wealthier, more educated people likely moved in as others moved out. But the census data alone can't show whether longtime residents were displaced or what the change meant to them, so interviews with residents would be needed to confirm it.
Common mistakes
- Treating quantitative data as more 'true' than qualitative data. Each answers different questions.
- Ignoring scale. A citywide average can hide sharp differences between neighborhoods.
- Drawing a cause from a correlation. Rising rents alongside new residents doesn't by itself prove displacement.
On the exam
- Expect a table or map of urban data. Describe the pattern with numbers from the source, then explain it with a course concept.
- A common part asks for a limitation of the data. Mention scale, sampling, missing context or what the data can't explain.
Connected topics
Videos
Check yourself
4 questions on 6.9 Urban Data. Pick an answer to see if you got it, and why.
| Measure | 2010 | 2020 |
|---|---|---|
| Median household income (2020 dollars) | 38,000 | 61,000 |
| Median monthly rent (2020 dollars) | 850 | 1,450 |
| Share of residents age 25–34 (%) | 18 | 31 |
| Share of residents who lived in the same home 10+ years (%) | 46 | 24 |
Hypothetical census and survey data for one urban neighborhood
Which conclusion is best supported by the data?
Which additional source would best show how longtime residents experienced these changes?
Which is an example of qualitative data a geographer might use to study a city neighborhood?
Which is the most important limitation of using national census data alone to study conditions in an informal settlement?
0 of 4 answered