Figure 218 Oct 2026From “What is the synthetic control method?”

California before Proposition 99: the real state, its synthetic version and the donor average

The synthetic California tracks the real one on past cigarette sales. The population-weighted average of the 38 donor states does not.

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Figure 2California before Proposition 99: the real state, its synthetic version and the donor average

Predictor	California	Synthetic California	Population-weighted average of 38 donor states
Cigarette sales per person, 1988 (packs)	90.10	91.62	114.20
Cigarette sales per person, 1980 (packs)	120.20	120.43	136.58
Cigarette sales per person, 1975 (packs)	127.10	126.99	132.81
Retail price (cents)	89.42	89.41	87.27
Beer consumption per person (gallons)	24.28	24.20	23.75
Percent aged 15–24	17.40	17.40	17.29
Ln(GDP per capita)	10.08	9.86	9.86

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Source: Abadie et al. (2010), Table 1, p. 499. Predictor means; all variables except lagged cigarette sales are averaged for 1980-1988 (beer consumption for 1984-1988). Cigarette sales in packs per person, retail price in cents, beer consumption in gallons per person. GDP per capita is measured in 1997 dollars; the authors' appendix describes the variable as logged per-capita state personal income. The third column is the population-weighted average of the 38 donor states (p. 499).

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A ADH10-C6 The population-weighted donor average is not a suitable control; the synthetic version reproduces California's values up to 1988, before Proposition 99; Table 1 gives the predictor means as real California, synthetic California and the population-weighted average of 38 states (GDP per capita in 1997 dollars, described in the appendix as logged per-capita state personal income): Ln(GDP per capita) 10.08, 9.86, 9.86; percent aged 15-24 17.40, 17.40, 17.29; retail price 89.42, 89.41, 87.27; beer consumption 24.28, 24.20, 23.75; cigarette sales 1988 90.10, 91.62, 114.20; 1980 120.20, 120.43, 136.58; 1975 127.10, 126.99, 132.81 (pp. 499, 500, 503): "the population-weighted average of the 38 states in the donor pool"; "GDP per capita is measured in 1997 dollars"; "Per-capita state personal income (logged)"; "does not seem to provide a suitable control group for California"; "the synthetic California accurately reproduces the values that smoking prevalence and smoking prevalence predictor variables had in California prior to the passage of Proposition 99"; "log GDP per capita does not have substantial power predicting the per capita cigarette consumption in California"Abadie, Diamond & Hainmueller. (2010)

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From the essay

From the research bench

What is the synthetic control method?

A synthetic control builds the missing comparison for one treated unit from a weighted mix of untreated ones. It only works if the mix fits the past.

18 Oct 2026

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Isoglu, S. (2026). California before Proposition 99: the real state, its synthetic version and the donor average [Figure]. isoglu.com. https://isoglu.com/insights/exhibits/isoglu-2026-what-is-the-synthetic-control-method-fig02/

BibTeX

@misc{isoglu-2026-what-is-the-synthetic-control-method-fig02,
  author = {Isoglu, Sinan},
  title = {{California before Proposition 99: the real state, its synthetic version and the donor average}},
  year = {2026},
  howpublished = {Figure 2, isoglu.com},
  url = {https://isoglu.com/insights/exhibits/isoglu-2026-what-is-the-synthetic-control-method-fig02/},
  note = {From the essay {What is the synthetic control method?}}
}

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<figure>
  <a href="https://isoglu.com/insights/exhibits/isoglu-2026-what-is-the-synthetic-control-method-fig02/">
    <img src="https://isoglu.com/social/isoglu-2026-what-is-the-synthetic-control-method-fig02.png" alt="Figure 2: California before Proposition 99: the real state, its synthetic version and the donor average" width="3200" height="2400">
  </a>
  <figcaption>Figure 2: California before Proposition 99: the real state, its synthetic version and the donor average. Source: Abadie et al. (2010), Table 1, p. 499. Predictor means; all variables except lagged cigarette sales are averaged for 1980-1988 (beer consumption for 1984-1988). Cigarette sales in packs per person, retail price in cents, beer consumption in gallons per person. GDP per capita is measured in 1997 dollars; the authors&#39; appendix describes the variable as logged per-capita state personal income. The third column is the population-weighted average of the 38 donor states (p. 499). <a href="https://isoglu.com/insights/exhibits/isoglu-2026-what-is-the-synthetic-control-method-fig02/">View exhibit</a>.</figcaption>
</figure>