What's the most widely planted white wine grape in the world?

Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.
Dear Dr. Vinny,
What's the most widely planted white wine grape in the world?
—Craig, Alberta, Canada
Dear Craig,
It’s always been difficult to get accurate, comprehensive information about worldwide grape acreage figures, because not every country tracks and reports this information in the same way.
However, in 2013 the University of Adelaide published Which Winegrape Varieties Are Grown Where? A Global Empirical Picture, by my new hero, economist Kym Anderson. It’s an amazing piece of research, tallying all the various pieces of information around the world and putting it together in a fascinating look at the trends in vineyard plantings.
According to the book, Airén is the most widely planted white grape variety in the world, which is kind of nuts because I’m sure most wine lovers haven’t heard of it. It’s widely grown in Spain (and Spain has the most vineyard acreage of any country), where it’s used for brandy, Sherry, and in white wines.
According to Anderson’s research, Airén used to be the most widely planted wine grape in the world, period, but since 1990, acreage has dropped dramatically, to about 250,000 acres in 2010. Anderson reports that the top five grapes planted worldwide are, in descending order: Cabernet Sauvignon (more than 700,000 acres), Merlot, Airén, Tempranillo and Chardonnay.
—Dr. Vinny