The economies of India and China could be larger than many people have thought. A new study from the World Bank now has some experts predicting that China will become the world's largest economy by one measure this year. The same study says that India's economy could pass Japan's as the world's third-largest.
印度和中国的经济可能会超出很多人曾经的想象。现在来自世界银行的一份报告使得一些专家预测说，今年中国将在一项指标上成为全球最大的经济体。而同一份研究报告称，印度将超过日本成为世界第三大经济体。
To get their results, the researchers used a different way to measure the size of a nation's economy. Usually economists measure by a country's Gross Domestic Product - the value of all goods and services it produces. But some say, a different method, called Purchasing Power Parities, or PPP is a better measure. It examines differences in the cost of living among nations.
为了获得他们的研究结果，研究人员使用了一种新的方法来衡量一个国家的经济规模。经济学家通常根据一国的国内生产总值来衡量。国民生产总值是指一国所生产的所有货物和服务的总价值。但也有人说，购买力平价（简称PPP）是一种更好的衡量方法。它调查各国的生活成本差异。
The report is from the International Comparison Program, which was established by the United Nations. The results are based on prices in 2011.
这份报告来自于联合国建立的国际比较项目（简称ICP），其结果是基于2011年的价格。
Kamel Mellahi is a professor at the University of Warwick in Britain. He says PPP provides economists with a way to compare the costs of ordinary things that people need in different countries.
卡梅尔·梅拉伊（Kamel Mellahi）是英国华威大学的一位教授。他说，购买力平价为经济学家提供了一种比较各国生活必需品的价格的办法。
"You take a basket of goods that we all buy, including milk, butter, sugar, [going] to the movies, prices of haircuts in different countries, and they look at the cost of that in different countries," Mellahi said.
梅拉伊说，“我们采用了一篮子大家都要购买的商品，包括各国牛奶、黄牛、糖，看电影和剪发的价格，并调查它们在不同国家的价格。”
Experts then establish a base exchange rate and use it to compare economies. The Gross Domestic Product measure uses market-based exchange rates to compare economies. They are exchange rates paid by travelers and exporters. So the main differences between GDP and PPP is how exchange rates are computed.
专家们然后建立一种基础汇率，并用它来比较经济。国民生产总值使用以市场为基础的汇率来比较经济，它指的是游客和出口商支付的汇率。因此，国民生产总值和购买力平价的主要区别是汇率如何计算。
Greg McBride is Chief Financial Analyst at Bankrate.com. He says PPP avoids some problems, but it is more like an estimate than a measurement.
格雷格·麦克布赖德（Greg McBride）是Bankrate.com网站的首席财务分析师。他说购买力平价避免了一些问题，但它更像是一种估计而不是衡量办法。
"There is a huge margin of error there that I think can really throw the validity of the whole thing into question," said McBride.
麦克布赖德说，“它存在巨大的误差范围，我认为这会让整体的有效性受到质疑。”
World Bank information shows that China's GDP was about $8 trillion in 2012, that was half the size of the $16 trillion US economy. However, Professor Mellahi says the GDP measurement underestimates developing economies.
世界银行的资料显示，2012年中国的国内生产总值约为8万亿美元，相当于美国16万亿美元经济规模的一半。然而，梅拉伊教授表示，国内生产总值衡量办法低估了发展中国家。
"People always said it underestimated the size of economies in developing countries, and some of the emerging economies," Mellahi said.
梅拉伊表示，“人们常说它低估了发展中国家和一些新兴经济体的经济规模。”
The economies of China and India continue to grow at rates higher than most developed economies. However, China and India rate far below other large economies when their economies are compared with their populations.
中国和印度的经济继续以高于大多数发达国家的速度增长。然而，当中国和印度的经济与其人口相比较，就远远低于其它大型经济体。