In 1973, U.S. per capita carbon dioxide emissions were 20 times those of China’s and 66 times those of India’s. By the year 2000, when many U.S. policymakers and consumers were aware of the effects of greenhouse gas emissions, U.S. per person emissions had dropped to just over 21 metric tons per year, while China’s and India’s had risen to 2.9 and 0.9 respectively. That meant U.S. per person emissions were seven times those of China’s and 23 times those of India’s. Since then, the United States' per person emission rate has continued to drop, but the country's 2021 per person carbon dioxide emissions were still nearly twice as large as China's and nearly 8 times as large as India's.