Eighty-four percent of the world's population had less than $20 to spend daily in 2011, an amount that puts them at or below the U.S. poverty line, reports a new Pew survey.

The world's middle class family of four lives on $10-20 per day, which translates to $14,600 to $29,200 annually, reports Pew. By contrast, the official poverty line in the United States in 2011 was $23,021 for a family of four. "Even those newly minted as middle class enjoy a standard of living that is modest by Western norms," said the report.

The study used purchasing power parities to account for differences in the cost of goods and services and exchange rates across countries. It compared 111 countries in 2011, the most recent year for which data is available, with 2001.

Poverty declined worldwide, but most of the world's poor failed to make it into the middle class. More than half the world's population (56 percent) remains "low income," which in 2011 meant they were living on $2 to $10 a day. Those who live on $2 a day or less fell from 29 percent in 2001 to 15 percent in 2011. At the same time, the share of low income earners making between $2-10 per day increased from 50 percent of the world's population to 56 percent.

Most people "only a moderate step up the income ladder," the Pew report said. However, the ranks of the world's middle class nearly doubled from 399 million people in 2001 to 784 million in 2011.

Most of the world population that is classified as upper-middle or high-income still lives in North America, Europe and the Asia Pacific region. In 2001, 91 percent of the world's high-income people lived in North America and Europe; in 2011, the number barely changed at 87 percent.

"The gap in living standards between the world's economically advanced countries and emerging and developing nations barely narrowed in the first decade of this century," said the report.

China, South America and Eastern Europe had some of the greatest regional increases in middle-income populations, in stark contrast with India, much of Asia, and Africa.

While the United Nation's Millennium Development Goals report stated earlier this week that the world's population making less than $1.25 a day halved between 1990 and 2015, the Pew study pointed out that most of these people are still poor and have not moved into the middle class.