German Chancellor Angela Merkel continues her reign as the most powerful woman on the planet for past nine years. Why? She clinched a third four-year term of Europe’s most vibrant economy in December 2014, making her the longest-serving elected EU head of state. She fought off a national recession during the global economic crisis with stimulus packages and government subsidies for companies that cut hours for workers, and she is in the thick of trying to help Greece revive its economy. She has used her power against ISIS, breaking the post-Nazi-era taboo of direct involvement in military actions by sending arms to Kurdish fighters. In the Russia-Ukraine crisis, she has been engaging in shuttle diplomacy trying to broker a peace deal with Vladimir Putin. There’s only one woman who has a chance of endangering her tenure as No. 1 in 2016 – and that’s the world’s No. 2 most powerful woman Hillary Clinton.

The presumptive Democratic front-runner in the 2016 presidential race is starting her campaign miles ahead of her challengers. Her Ready for Hillary super PAC raised $9 million in 2014 and some of her biggest potential donors have yet to commit. A recent CNN/ORC poll, seven out of 10 Democratic voters favored her, while her closest Republican contender, Marco Rubio, trailed her by 12 points. She is the first and only first lady to become a U.S. Senator, not to mention presidential candidate. Her bestselling 2014 memoir, “Hard Choices,” which chronicles her time as Secretary of State, reportedly earned her a high-seven-figure advance. Her popularity remains high despite the “emailgate” revelations that she used her own private email address and server while Secretary of State, instead of the government system, potentially making her correspondence vulnerable to hacking and foreign surveillance. She has said she regretted the decision and complied with government rules. In September 2014 she marked a personal first, the birth of her grandchild, Charlotte Clinton Mezvinsky.

Melinda Gates has cemented her dominance in philanthropy and global development to the tune of $3.9 billion in giving in 2014 and more than $33 billion in grant payments since she founded the Bill & Melinda Gates Foundation with her husband in 2000. Her work has inspired other big donors and has changed way funders think about effective philanthropy: highly targeted campaigns coupled with data-driven monitoring and global collaboration. As the woman with her name on the door, Gates decides the direction of the organization and reviews the results. Much of her attention is now focused on championing investments in women and girls around the world.

Janet Yellen made history in 2014 when she became the first female head of the Federal Reserve.  The Yale and Brown educated economist has barely had a moments rest since then: She took over shortly after the central bank began unwinding its recession era bond buying program and then deftly ushered markets through six cuts that brought monthly purchases to $0 from a peak of $85 billion. Now the Fed is on track to loosen the economic reigns further by beginning to hike interest rates as soon as June 2015 — a feat it hasn’t attempted since 2004. With so much at stake a single word from Yellen can send asset prices swinging but she received praise in March 2015 when she managed to change guidance without spooking investors. Meanwhile she has been fighting a call to increase congressional supervision of the Fed while pushing to improve the Fed’s oversight of big banks.

Mary Barra survived a harrowing first year as the first woman ever to head a Big 8 automaker last year. She faced revelations about faulty ignition switches blamed for at least 74 deaths and 126 injuries, a 30-million car recall and pressure from investors to return more cash to shareholders. In October the 35-year GM veteran finally got to lay out her strategy for the future, which includes turning Cadillac into a global luxury brand, continuing to grow in China and becoming a technology leader. Under Barra GM is also proving to be more disciplined financially, making tough decisions like pulling out of Russia, Australia and Indonesia or killing the Chevrolet brand in Europe if there’s not enough profit to justify continued investment.

Christine Lagarde is entering  the last year of her first term heading the International Monetary Fund, the organization which serves as economic advisor and backstop for 188 countries. When she took over in 2011 the world economy was still recovering from the financial crisis. Today Lagarde is projecting 3.5% annual global growth — only a hint above last year’s rate and down from 4% in 2011. Lagarde calls this the “new mediocre” and is vocal about her concern that slow growth has become the “new reality.” How is the IMF helping? By viewing emerging markets as unique locals rather than a single entity and warning central bankers ? the U.S. Federal Reserve especially ? to be wary of the potential negative effects of differing monetary policy across the globe. Under Lagarde the IMF has supported efforts to increase female labor force participation as way to reduce poverty and inequality.

Calls for President Dilma Rousseff’s resignation were chanted through the streets of Brazil at the start of this year, just months into her second term. Rousseff, who ran on campaign promises to harness oil and boost the economy, is now battling a bribery scandal that involves the national oil company Petrobras. As Brazil’s first female president, she was elected in 2010 and was on track to end poverty in the world’s seventh-largest economy. But the hopes of her supporters have fallen flat in recent months as her approval ratings have dropped to 13%. Additionally, the economy of the country with a GDP of $2.19 trillion could shrink for the second consecutive year.

Facebook Chief Operating Officer Sheryl Sandberg knows how to command attention. Her 2013 bestseller, “Lean In,” won famous fans including Yahoo CEO Marissa Mayer and Beyonce, spawned thousands of Lean In Circle support groups, inspired a spin-off, “Lean In for Graduates,” published in 2014, and a Sony Pictures movie deal. The mother of two is a former Google executive, wooed in 2007 to Facebook by billionaire founder Mark Zuckerberg to the fledgling startup run by college dropouts. Before Google, the Harvard MBA worked as chief of staff to then-Treasury Secretary Larry Summers. She is a significant shareholder and oversees sales, marketing, business development, human resources and communications at the social media giant. Under Sandberg’s leadership, Facebook has improved its earnings performance and revamped its mobile strategy. She recently joined The Giving Pledge, promising to give away at least half of her net worth to charitable causes. Her husband, SurveyMonkey CEO Dave Goldberg, died unexpectedly of head trauma after a fall on a treadmill in early May. He was just 47 years old.

Memes may come and go, but Wojcicki’s new job is to make certain YouTube profits from every one of them. Google employee No. 16 — the company started in her Menlo Park garage — now heads up the Internet’s central hub for all things video. In February 2014, Wojcicki moved from her post as consigliore for Google’s ads and commerce (some 90% of revenue) to become CEO of the world’s largest video platform. It was a long time coming: In 2006, Wojcicki championed the $1.65 billion acquisition now valued at some $20 billion with revenues projected to be $5.6 billion last year, up about 51% from the past year. With more than 1 billion UVs per month and more eyeballs among adults 18 – 34, the former ad chief is quickly focusing on new ad formats, campaigns and market share. Calling YouTube complementary to television, Wojcicki is working to support YouTube’s celebrities and help media companies make the most of the video platform.

While her husband may sit in the Oval Office, First Lady Michelle Obama has her own power seat in the White House. At the start of the year, she traveled to Southeast Asia to push an initiative that aims to get more girls educated and therefore improve the well-being and financial stability of young women. In the summer of 2014, she spoke of the administration’s effort to end homelessness among military veterans in the U.S. — cities like Phoenix and Salt Lake City have been successful — and pushed back against measures that would allow some schools to opt out of the federal dietary standards for school lunches. Obama gained attention after opting not to cover her head during a visit with the president to Saudi Arabia.

Credit: Forbes.com