Environmental protection is important for all nations, as discussed in Chap. 2 . In preparing a policy to combat the climate change, so enhancing the level of ESG and SDGs, we use a new approach whose assessment is useful for promoting both sustainable development and green growth economy. The approach also assesses a technological progress over time, focusing upon pollution reduction. The methodology used in the approach is DEA-EA discussed in Chaps. 5 and 6 . In this chapter, we apply DEA-EA to 37 OECD countries during 1995–2014, examine performance differences among country groups, and then discuss their convergences to multiple subgroups in a long run. Such convergence indicates an invariant status of their SDGs performances. As an extension of a previous study (Sueyoshi and Wang, Journal of Cleaner Production 250:1–13, 2020), which has compared between OECD and Non-OECD nations, this study focuses upon only OECD and examine whether we can find club (core group) convergences among the member nations. The DEA-EA, used in this chapter, examines whether OECD can provide member nations with an opportunity to improve the status of their green technology along with their economic growths. The underlying concepts incorporated into DEA-EA are UEM (Unified Efficiency) and UIM (Unified Index), both are under managerial disposability. The UIM finds a technology shift more clearly than the UEM. The UEM incorporates SDGs in a time horizon and the UIM extends it more clearly from a technology shift on environmental protection. Our empirical results indicate that there is the overall convergence of OECD nations in UEM, but we cannot find it in UIM. They are classified into two clubs in the UIM convergence assessment. The results indicate that there are uneven economic and environmental progresses between the two (higher and lower) member groups. The disparity implies that OECD membership does not guarantee uniform green growth and sustainable development for their developments for SDGs. We also find that “renewable and nuclear” energy shares are important for maintaining the higher group within OECD because both are energy sources with zero carbon emission.