How fast is the English language expanding?

Recent research suggests that the English language has doubled in size over the last century. It continues to grow 'by 8,500 words a year and now stands at 1,022,000 words.'

The pace of this growth is accelerating, with the word count  expanding by more than 70 per cent since 1950. In the previous half century it only grew by 10 per cent. 

This is part of general trend towards globalisation. As English terms enter other languages there has been some reciprocation. An increasing number of loanwords now describe imported concepts: feng shui, from Chinese, for example.

Science & Technology

Another factor has been the creation of new vocabulary categories to describe advances in science and technology. These often draw on existing loanwords. Digital, for example, comes from the Latin for digit or finger.