19.3 Canonical designs

clever designs, but context-dependent

• judge designs –> harshness of judgments
• military drafts –> being in the army
• compulsory schooling –> years of schooling
• Bartik shift-share IV (combine economy-wide trends with distribution of industry)
• locations of original immigration wave –> location of later immigrants
• twin births –> number of children
• direction of wind –> pollution