Table 1. Turning points reached in previous studies, by type of pollutant.
| Pollutant type | Study | Dataset | Period | Econometric technique | Turning point |
|---|---|---|---|---|---|
| Greenhouse gas emissions | [6] | 108 states | 1951–1986 | Fixed effects regressions | 35,428 (in 1986 U.S. $) |
| Greenhouse gas emissions | [34] | OECD and non-OECD states | 1960–1998 | Weibull specification | 15,599.90–21,185.83 (in 1990 U.S. $) |
| Greenhouse gas emissions | [35] | 16 metropolitan regions in Korea | 1990–2005 | Fixed effects and random effects regressions | 26,400–30,000 (in 2000 U.S. $) |
| Greenhouse gas emissions | [36] | 12 Middle East and North African states (MENA) | 1981–2005 | Panel Error-Correction | 37,263 (in 2005 international $) |
| Greenhouse gas emissions | [25] | Spain | 1874–2011 | Autoregressive distributed lag (ARDL) | 8,103 (in 1990 U.S. $) |
| Greenhouse gas emissions | [37] | 136 states | 1971–2010 | Ordinary least squares (OLS) with heteroskedasticity-robust standard errors | outside the sample and statistically insignificant |
| Greenhouse gas emissions | [38] | China | 1970–2015 | Auto regressive distributed lag (ARDL), fully modified ordinary least squares (FMOLS), dynamic ordinary least squares (DOLS) and impulse response and variance decomposition | 744,665 (in 2010 U.S. $) |
| Greenhouse gas emissions | [39] | Morocco | 1966–2014 | Ordinary least squares (OLS) | 7,800 (in 2010 U.S. $) |
| Emissions of sulfur oxides | [40] | Cross-section of urban areas located in 42 countries | 1977; 1982; 1988 | Random effects regressions | 4,000–5,000 (in 1985 U.S. $) |
| Emissions of sulfur oxides | [41] | 149 states | 1960–1990 | Ordinary least squares (OLS) | 3,670 (in 1985 U.S. $) |
| Emissions of sulfur oxides | [42] | 55 states | 1987–1988 | Ordinary least squares (OLS) | 2,900–3,800 (in 1985 U.S. $) |
| Emissions of sulfur oxides | [43] | 30 states | 1979–1987 | Fixed effects regressions | 8,700–10,700 (in 1990 U.S. $) |
| Emissions of sulfur oxides | [44] | 58 Turkish provinces | 1992–2001 | Pooled EGLS (cross-section weights) | 1,934 and 5,817 (in 2000 U.S. $) |
| Emissions of sulfur oxides | [45] | Tunisia | 1961–2004 | Johansen cointegration | 1,200 (in 2000 U.S. $) |
| Emissions of sulfur oxides | [35] | 16 metropolitan regions in Korea | 1990–2005 | Fixed Effects and Random Effects Regressions | 5,700 and 28,000 (in 2000 U.S. $) |
| Emissions of sulfur oxides | [37] | 136 states | 1971–2010 | Ordinary least squares (OLS) | 112,000 (in 2005 PPP adjusted U.S. $) |
| Emissions of nitrogen oxides | [42] | 55 states | 1987–1988 | Ordinary least squares | 5,500 (in 1985 U.S. $) |
| Emissions of nitrogen oxides | [35] | 16 metropolitan regions in Korea | 1990–2005 | Fixed Effects and Random Effects Regressions | 27,600 (in 2000 U.S. $) |
Source: Authors’ compilation based on literature review.