What does it mean to be socially vulnerable?

EPID 684
Spatial Epidemiology
University of Michigan School of Public Health

Jon Zelner
[email protected]

Theme for this week


  • Where did the social vulnerability index come from, anyway?

  • Do we need summary measures like the SVI to get at these questions?

  • Project time

A brief history of social vulnerability

  • An idea originally from natural disasters 🌪️ research.

  • Focused on characterizing the social determinants of resilience.

  • Originally used to highlight places potentially at risk rather than as a model-based predictor of risk.

Inspired by the hazards-of-place framework

An explicitly spatial measure

Social vulnerability is partially the product of social inequalities — those social factors that influence or shape the susceptibility of various groups to harm and that also govern their ability to respond. However, it also includes place inequalities—those characteristics of communities and the built environment, such as the level of urbanization, growth rates, and economic vitality, that contribute to the social vulnerability of places. (1)

Constructing the original SoVI

  • 250+ variables originally drawn from 1990 decennial census for each U.S. county

  • Since many of these were highly correlated, this original set was reduced to 85 input variables.

  • Principal components analysis (PCA) was used to collapse these into a set of independent factors that characterize different dimensions of vulnerability.

  • Each county assigned a score based on its census characteristics.

What is PCA?

PCA separates a potentially correlated data matrix into orthogonal components (Image from this blog post)

Can be used to identify clusters

Emergent clusters identified by plotting two independent principal components against each other

SoVI Components

How can we intepret the fact that these are the key dimensions of vulnerability identified by (1)

SoVI ca. 1990


How have the key dimensions of social vulnerability changed over time?

What (if anything) does this tell us? (2)

How are these patterns reflected spatially?


Spending some time with the SoVI

The handy-dandy hands-on SoVI map

Some things to try

  • Pick a state

  • Look at the spatial distribution of SoVI across census tracts and counties

  • How does this change as a function of scale?

  • How does it change when the state is the frame of reference vs the whole country?

What are some potential problems with the SoVI?

Weights are very sensitive to the inclusion of geographic areas and time periods (Example from (3))

Social vulnerability \(\to\) 🫀 vulnerability

What are some key takeaways from this result? (From (4))

What does this tell us about the relationship between vulnerability and COVID-19 risk?

What appears to be the most relevant spatial scale of variation in (5)


Cutter SL, Boruff BJ, Shirley WL. Social Vulnerability to Environmental Hazard. Social Science Quarterly [electronic article]. 2003;84(2):242–261. (https://onlinelibrary.wiley.com/doi/abs/10.1111/1540-6237.8402002). (Accessed April 12, 2023)
Cutter SL, Finch C. Temporal and spatial changes in social vulnerability to natural hazards. Proceedings of the National Academy of Sciences [electronic article]. 2008;105(7):2301–2306. (https://www.pnas.org/doi/10.1073/pnas.0710375105). (Accessed April 12, 2023)
Spielman SE, Tuccillo J, Folch DC, et al. Evaluating social vulnerability indicators: Criteria and their application to the Social Vulnerability Index. Nat Hazards [electronic article]. 2020;100(1):417–436. (http://link.springer.com/10.1007/s11069-019-03820-z). (Accessed April 5, 2023)
Khan SU, Javed Z, Lone AN, et al. Social Vulnerability and Premature Cardiovascular Mortality Among US Counties, 2014 to 2018. Circulation [electronic article]. 2021;144(16):1272–1279. (https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.121.054516). (Accessed April 10, 2023)
Fletcher KM, Espey J, Grossman MK, et al. Social vulnerability and county stay-at-home behavior during COVID-19 stay-at-home orders, United States, April 7–April 20, 2020. Annals of Epidemiology [electronic article]. 2021;64:76–82. (https://linkinghub.elsevier.com/retrieve/pii/S1047279721002805). (Accessed April 10, 2023)