Estimated number of students studying Spanish worldwide: 15 to 16 million

From another article here in Spanish, this one from two weeks ago. Here's part of it:

Spanish is the second foreign language most in demand in Europe and has a total of 16 million students throughout the world, according to data given today by the head of diplomas of the Instituto Cervantes, José Ramón Parrando.

The institute said that the demand for Spanish is growing every day and that it is not possible to meet all the demand for new offices in different countries.

According to their explanation there are between fifteen and sixteen million students of Spanish throughout the world, most of them taking it in formal education. It also added that Spanish is "clearly moving" to take the place of French in Europe as the second foreign language after English.

The Instituto Cervantes intends to turn Spanish into a global language and to reach the level currently occupied by English in international diplomacy, scientific investigation and trade.

"We are not in a race with English, but I do believe that in a few years we will be in a very favorable situation compared to other European languages that have had a considerable geographic extent, but have not had the luck Spanish has had..." said Parrondo.