John Snow’s 1854 London Cholera Map

• A severe outbreak of cholera in 1854 near Golden Square in Soho, London killed 616 people
  • Germ theory of disease is not yet widely accepted
• Miasma theory
  • Miasma = ”bad air” or “noxious vapours” from rotting organic matter
  • People thought disease spread through smell and dirty air
• But no one knows why only certain districts are affected
  • If it was just “bad air”, why would some streets be badly hit and others nearby almost untouched?

• Physician John Snow proposes an alternative theory of germ-contaminated water:
  • Mapping the contaminated districts
  • Mapping the water supply and pump system
  • Deaths cluster around one particular pump in Broad Street
  • Workers at a brewery did not get sick: they drank too much beer instead of water
• A new field of spatial epidemiology and improved sanitation facilities
  • Today: COVID-19, malaria, bird flus

Housing prices

• House prices in the same neighbourhood tend to be similar
• Perhaps due to shared environmental, social, or economics conditions
  • Air quality
  • Flood risk
  • Noise from roads
  • Access to green areas
  • Crime rates
  • Community facilities
• Oxford: £501,992
• Cambridge: £498,163
  • We beat them!

UK House Price Index England: August 2025

Tobler’s First Law of Geography (1970)

<aside> 💡

Everything is related to everything else but near things are more related than distant things.

</aside>

• A foundational concept in the field of spatial analysis
  • Introduced by geographer Waldo Tobler
  • Location matters
  • Distance weakens the relationship
• Spatial interpolation
  • Predicts unknown values based on known values at nearby locations
• Spatial regression models
  • Takes into account the spatial dependence between observations

The end of Ordinary Least Squares Regression

• Used to relate one variable to several others
• Drawing the best-fitting line through a cloud of points