Efficiency in stock markets is essential for economic stability and growth. This study investigates the efficiency and herding behavior of the stock markets from the top economies of the world (known as G20 countries). We classify stock market indices using MSCI classification for the developed and emerging markets to provide a comparative examination using the latest data and by employing the robust multifractal detrended fluctuation (MFDFA) method. In addition to the full sample, the analysis uses sub-sample periods to reveal the hidden features and efficiencies of the G20 markets during the Russia–Ukraine War and COVID-19 for the first time. The findings show the availability of varied multifractality among all G20 stock markets during the overall and crisis periods, exhibit long-range correlations, and may support the fractal market hypothesis. In addition, Italy remains the least efficient, while Germany remains the most efficient stock market. The sub-sample results further reveal unevenness in the local fluctuations and resultant higher inefficiency considering the sheer magnitude and impact of crises on the G20 stock markets. However, the efficiency of developed stock markets performed better as compared to emerging markets. The study of G20 stock markets is useful and provides several implications for a wider audience.

This paper discusses the role of afforestation projects and other climate technologies in the green agenda for Russia and aims to justify the anchoring of jurisdictional carbon pricing in the cost approach to valuation, specifically, with reference to the cost economics for afforestation projects given their centrality to the agenda. Through that, and due to the inchoate state of carbon pricing in the study jurisdiction, this paper aims to advance price discovery for national carbon credits in both compliance and voluntary schemes. The cost approach framework, moderated by international market comparisons, indicates the fair price of carbon in Russian jurisdiction at the level of USD 20–25 per tonne of CO₂-eq, which is close to the global median but is more than double the amount of carbon levies set under the Sakhalin GHG quota experiment. It is argued that unless such a fair price for carbon is set in the country, the national carbon credits market will not achieve viable growth, nor will sustainable development be advanced, and funds for it be adequately collected. This represents a relevant contribution to the literature on the development of the national carbon credit markets.