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  1. In the 1980’s the rate of increase of the minority population of the United States was nearly twice as fast as it was in the 1970’s.
  2. In the 1980’s the rate of increase of the minority population of the United States was nearly twice what it was in the 1970’s.
  3. In the 1980’s the rate of increase of the minority population of the United States was nearly two times faster than that of the 1970’s.
  4. In the 1980’s the rate of increase of the minority population of the United States was nearly two times greater than the 1970’s.

Can anyone explain correct grammatical sentence between these ?

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    A usage does not need "solid ground"; it simply needs to occur. Most idioms don't make sense syntactically, and many don't make any sense except on some metaphoric level. In particular, equatives, comparatives, and superlatives are full of strange grammar. Aug 11, 2012 at 14:57

4 Answers 4

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This is a lexical matter: 'rate' is a measure of speed, so in formal discourse it gets bigger or larger rather than faster - it's the increase which gets faster.

There are, however, less cumbersome ways of expressing this:

In the 1980s the minority population of the United States

  • grew twice as fast as it had in the 1970s. OR
  • grew two times faster than it had in the 1970s. OR
  • grew at twice (or two times or double) the rate it had (grown) in the 1970s.
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    And there is some ambiguity in "times faster" ... Ten percent faster means 1.1 times as fast... One hundred percent faster means 2 times as fast... Two hundred percent faster means 3 times as fast... But does "two times faster" mean 2 times as fast or 3 times as fast ??
    – GEdgar
    Aug 11, 2012 at 13:20
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    Also, one could use "double" ~ grew at double the rate it had grown in the 1970s
    – J.R.
    Aug 11, 2012 at 13:57
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    @GEdgar That's a good question. I'd say the 'times' tells you to multiply the base value by the value named, while x% faster means add the value named to the base value. That's how I've always read/used it; but if there's a consensus that it's ambiguous I'll modify my usage and my answer. Aug 11, 2012 at 13:58
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    @J.R. Good point - I'll add that to my answer. Aug 11, 2012 at 13:59
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    Yes, one often sees comments like 'The population has risen by 700%' when in actual fact it has risen by 600% - eg from 10 million to 70 million. The 'by 100%' analogue is always understood to mean a doubling. In maths, it is common to use 'increased, scale factor 7' (ie multiply the base figure by 7) to avoid this confusion. 'Increased sevenfold' is a less technical-sounding equivalent. The trouble here is that 'increase by ___' grammatically requires the size of the increase to follow, but is generally misused. 'Go with the concensus' wouldn't work as no-one has ruled at what %ge to switch! Aug 11, 2012 at 21:52
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There is no difference in meaning between two times and twice, only a slight difference in usage.

If you have to pick between them, choose twice, because it is the special, dedicated word that means two times over. In all these examples, it sounds more natural to use twice, perhaps especially in the last pair:

  • My car is twice as fast as yours.
  • My car is two times faster than yours.

  • I ran twice as fast as you.
  • I ran two times faster than you.

  • I’ve already called them twice now.
  • I’ve already called them two times now.

Twice is just the word for two times. The word for just one time is once. The word for three times is thrice. There is no word for four times, as this question reveals.

That’s really all there is to it.

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To answer your question more directly:

  1. In the 1980’s the rate of increase of the minority population of the United States was nearly twice as fast as it was in the 1970’s.

    • A rate of increase cannot be "faster" only greater as stated by StonyB
  2. In the 1980’s the rate of increase of the minority population of the United States was nearly twice what it was in the 1970’s.

    • This is perfectly correct
  3. In the 1980’s the rate of increase of the minority population of the United States was nearly two times faster than that of the 1970’s.

    • A rate of increase cannot be "faster". Also, as some have noted; 0.5 times faster than n is not the same 0.5 times as fast as n. But this has no bearing on the grammatical correctness.
  4. In the 1980’s the rate of increase of the minority population of the United States was nearly two times greater than the 1970’s.

    • This is missing a pronoun. Eg. "the 1970's" cannot be compared to a rate of increase.
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"Two times as fast" is the same as "twice as fast". But "two times faster" is the same as "three times as fast", for the same reason that "100% faster" is the same as "twice as fast".

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  • "'two times faster' is the same as 'three times as fast'" 2≠3 Feb 15, 2013 at 20:26
  • actually he is trying to give away mathematical reasoning here, which in his context are not wrong. But in reference to the question they are wrong. I guess!
    – camelbrush
    Feb 15, 2013 at 22:53

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