The English language was introduced to the Americas by British colonisation, beginning in the late 16th and early 17th centuries. The language also spread to numerous other parts of the world as a result of British trade and colonisation and the spread of the former British Empire, which, by 1921, included 470–570 million people, about a quarter of the world's population. Written forms of British and American English as found in newspapers and textbooks vary little in their essential features, with only occasional noticeable differences.