English, of all languages, is spoken the most in the world.
English is the official or principal language of 27 large countries, plus 35 small countries, and is one of the official languages in India and South Africa. This makes 64 countries where official communication is in English. There are between 500,000,000 and 1,000,000,000 NATIVE English speakers. In many other countries, almost everyone can speak English to some degree, especially in the cities. So, the TOTAL number of English speakers is much higher.
It is POSSIBLE that Mandarin has more NATIVE speakers, but they are mainly in China. Even in China, not everyone speaks it. Wikianswers states: “Within China, however, only about 53 per cent of the population can communicate in Standard Mandarin.” (That is about 636,000,000 people.)
As a further comparison, French is an official language in 36 countries, Arabic in 21 countries, and Spanish in 22 countries. These languages, plus Hindi, Bengali, Portuguese, and Russian have about 200,000,000 to 500,000,000 speakers in each. Malay/Indonesian, German, Japanese, Farsi, Urdu, and Punjabi have about 100,000,000 - 200,000,000 speakers in each. If you learn these 15 languages, you could go to most countries in the world and be able to communicate in the official language, OR, with just English ability, you would find many people in any major city of the world that you could communicate with.
Other reasons are that English is easier to learn for Spanish speakers than some other languages, especially Mandarin, and most useful documents and many works of literature, music and art are in English, many of them only in English.
In summary, although English is NOT the world’s best language (with many confusing and contradictory features and hard-to-pronounce sounds), it is the best choice for a second language for anyone in the world who does not already speak it.
For the Outsourcing, English is the designated language when there are managers, engineers and clients from different countries. It is important to have clarity at each level of the process, from customer requirements and technical specifications to management decisions. During the execution of a project, maintaining unclear communication will generate frustration, lack of credibility, disorder and low level of productivity. For this reason, the company AssureSoft that develops software in Bolivia invests in the English of its engineers and in that of general staff with a private tutor in the office, in addition to the option of taking classes in the best institutes of Cochabamba.