• By 2008, the percentage of students choosing science subjects had decreased markedly.

Why don't we use "in" instead? I'm a non-English native speaker, and I don't know the differences between those two prepositions when they go with year.

  • 2
    By 2008: there's another year or time period that is under discussion (say 1994) and the numbers decreased a lot between 1994 and 2008. In 2008: the numbers decreased between 2007 and 2008. Sep 11, 2016 at 16:48
  • Have you looked up by in a dictionary? Oxford has this sense of the word as definition #4, for example, which should make it quite clear why in is not used here. Sep 11, 2016 at 17:06

1 Answer 1


'In' as applied to a year refers to something which occurs or occurred in that year. For example "The last London Olympics took place in 2012". 'By' has the meaning of 'up to' or 'up to and including'. For example "The internal combustion engine was invented in the late 19th century and by 1930 was the main power source for mechanised road vehicles".

The use of 'by' in the quotation you gave suggests that the there has been a decline in the percentage of science students over a number of years. If 'in' had been used it would have implied that the decline took place between 1st January 2008 and 31st December 2008.

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