单选题：阅读材料，回答题。Extensive new studies suggest that the world has m

阅读材料，回答题。
Extensive new studies suggest that the world has made extraordinary progress in reducing poverty in recent decades. The research suggests that the pace of economic progress has been rapid and continued for decades, built on the foundations of relative political stability, rising trade, and economic liberalization (自由化) after two world wars. One new study, published recently by the Institute for International Economics in Washington, find that the proportion of the 6.1 billion people in the world who live on $1 a day or less shrank from 63 percent in 1950 to 35 percent in 1955and 12 percent in 1999. By some other measures, the progress has been more modest. Still, economists agree that poverty has plunged in key nations such as India and especially China, thanks to slowing population growth as well as economic freedom. "This is a huge success for the world as a whole," says Harvard University economist Richard Cooper. "We are doing something right. "
The news comes as the World Bank is about to open its annual meeting in Washington an event that has been troubled in recent years by protests that the Bank and its sister Institution, the International Monetary Fund(IMF 国际货币组织） have done too little for the world’s poor. The new economic research will not put an end to that dispute. Vast populations remain poor, and many still question the wisdom of World Bank policies. Nonetheless, the research findings are helpful to understand what policies should be followed by those institutions and hundreds of other development groups working very hard to hasten the pace of world economic progress. If dramatic gains are under way, the present policies calling for open tharkets, free business activities, and tight monetary control are working and correct.
But critics of IMF and World Bank policies maintain that such economic success stories as Japan, China, South Korea and Singapore are rooted in more than just "free" markets. These nation shave managed to grow rapidly, and thereby reduce poverty, by limiting imports when their domestic industries were young, pushing exports to rich nations, and putting controls on purely international financial flows. The have been open to foreign owned factories but have often insisted that those investors share the knowledge and skill on modern technologies.
The word "plunged" in the first paragraph means__________. A．decreased
B．climbed
C．increased
D．dropped into water