Learn English – Difference between (in / for / ∅ / during / over) the (past / last) three years

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Microsoft has steadily improved its operating cash flows in the past three years.

Microsoft has steadily improved its operating cash flows in the last three years.

Microsoft has steadily improved its operating cash flows for the past three years.

Microsoft has steadily improved its operating cash flows for the last three years.

Microsoft has steadily improved its operating cash flows for the past three years. ("for" omitted)

Microsoft has steadily improved its operating cash flows for the last three years. ("for" omitted)

Microsoft has steadily improved its operating cash flows during the past three years.

Microsoft has steadily improved its operating cash flows during the last three years.

Microsoft has steadily improved its operating cash flows over the past three years.

Microsoft has steadily improved its operating cash flows over the last three years.

Which of them are idiomatic and preferred? Are they interchangeable?

Best Answer

Each of the examples above is grammatically correct, but with a slightly different meaning.

First, the question of "past" or "last" is less important, and it may depend on context. To me, "past" means specifically that each of the three years in question has already ended, whereas "last" might include the current year. Context is more important than the choice of words here.

The phrasing is more important. This is somewhat subjective, but to me the different prepositions indicate these connotations:

  • "... in the past/last three years": Cash flows steadily improved during some interval of these years
  • "... for the past/last three years": Cash flows started improving three years ago and never stopped
  • "... the past/last three years": Same as "for", but a bit awkward to my ears
  • "... during the past/last three years": Same as "in"
  • "... over the past/last three years": Probably the same as "for", but now there is some ambiguity. "Over" could be a comparison between the current improved cash flow and that of the previous three years.
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