US President Barack Obama tops again Forbes magazine's 2012 annual ranking of the world's most powerful people.

According to the publication, Obama has earned points for his reelection for second term in office, thus securing the opportunity to carry out his political ideas for another 4 years.

Obama is followed by German Chancellor Angela Merkel and Russian President Vladimir Putin, who was second in 2011.

The list contains 71 names, a figure "Forbes" said it chose because there are an estimated 7.1 billion people in the world and thus the ranking works out to one very heavy hitter for every 100 million people.

Also among the top spots are Microsoft founder and philanthropist Bill Gates, Pope Benedict XVI, and two bankers -- US Federal Reserve Chairman Ben Bernanke and European Bank President Mario Draghi.

King Abdullah of Saudi Arabia and two politicians, British premier David Cameron and Chinese Communist Party General Secretary Xi Jinping, complete the top 10.

As in 2011, the youngest participant in this year's list is 28-year old founder of Facebook Mark Zuckerberg, who climbed to 9th place in last year's vote, but now is 25th. Media mogul Rupert Murdock is 26th.

Forbes' list of criteria for compiling the annual top 70 list include the number of people under a person's power; the financial resources they control; the breadth of their influence over more than one area; and how actively the person wields their power.