English is not my mother tongue. The question is whether the phrase "half as fast" is grammatical, frequent and unambiguous.

When googling, I've found out that the structure "verb + half as fast as" is frequent. But the search results for "verb + half as fast" are not convincing.

In January the growth of corporate loans was __%. In December the growth of corporate loans was half as fast, and the corporate loans in total increased by 5.6%. (by means addition or subtraction, half as fast means twice as slow).

Half as fast is relating to the growth (the rate of the increase). The percentage value 5.6 is relating to the increase in the corporate loans. The increase is equal to 5.6%. The rate of the increase in December is half as fast as the value measured in January.

  • 1
    Is there a question? Commented Jul 6, 2015 at 14:09
  • Sorry for incorrect formulation. I edited the question.
    – user128024
    Commented Jul 6, 2015 at 14:34
  • 1
    If 5.6% represented a "half as fast" increase, then the original would have to be 11.2%. Half as fast means at a rate half the original comparator. Twice as fast would mean double the rate or, in this case, 22.4%.
    – Robusto
    Commented Jul 6, 2015 at 14:48
  • @Robusto I edited the question.
    – user128024
    Commented Jul 6, 2015 at 17:53

1 Answer 1


"Half as fast" is definitely in common use, meaning that the velocity (here of the growth in corporate loans) is half as much as previously referenced. The paragraph is confusing for a number of reasons:

  • The phrases aren't in chronological order, which is especially important when you give a quality of the second phrase in terms of the first (e.g. "Today I ran a 5 minute mile; yesterday I was much slower" is a bit weird).
  • It isn't clear whether the item that increased by 5.6% is "corporate loans", or "the growth of corporate loans"
  • "increased" should be "increasing"

I've seen "twice as slow" used occasionally, but always in confusing and contradictory ways; I'd avoid it.

  • Thanks. I edited the question because the initial formulation was incorrect. Please see the corrected question.
    – user128024
    Commented Jul 6, 2015 at 17:50
  • The presence of "... as XXXX" is a separate issue. You can say "X is half as fast as Y", but if you say "X was moving at rate R, but later was moving half as fast" then you're implying the "... as" part: "... was moving half as fast as X was previously moving". Commented Jul 6, 2015 at 18:46

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