When you achieved something is very important because it provides context for the reader. I often see resumes where the person has held the same position for 10-15 years or so, and they say something like "Achieved less than 1% shrink."
I automatically ask myself, when? This year? Last year? Three years ago? Fifteen years ago?
Or, how often? Every year? Twice? Five times?
Because there's no context, the achievement itself means very little to the reader. This is why it's very important to include your achievements within each position in your work history, not in a separate "Achievements" section.
Hope that helps!
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