I don't quite understand the things in bold:

Of the 40 occasions since 1928 in which an industry rose by at least 100% over any two-year period, a collapse of more than 40% over the subsequent two years occurred 53% of the time — or 21 times, as noted above.

Source: http://www.barrons.com/articles/are-we-in-a-stock-market-bubble-1490261265?google_editors_picks=true

There are lots of things that are confusing. Does "40% over the next two years" mean the same as "40% of the next two years"?

Does 53% of the time mean "50% of the two years"?

If so, how does the meaning of the whole sentence fit together?

  • 4
    This question is off-topic because it is about how to understand percentages.
    – TimR
    Mar 26, 2017 at 10:34
  • 2
    @TRo I don't think this is any different from other comprehension questions. It's not about what "53 %" means but what it's referring to.
    – M.A.R.
    Mar 26, 2017 at 10:51
  • 1
    Your question does not say what it is about the language that makes it difficult for you to understand the passage. That you cannot get your head around the numbers is not relevant here.
    – TimR
    Mar 26, 2017 at 11:08
  • 2
    @haile Please be nice, and try to focus on the question itself when commenting, not on other users. Comments of that nature about other users are not acceptable here, but you can certainly explain why you feel your question is on-topic, as M.A.R. does in his comment.
    – user230
    Mar 26, 2017 at 11:09
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    I agree with @TRomano. I can see how this sentence might be confusing, but OP hasn't given any information what, exactly, is most problematic -- for example, haile could offer a "best guess". Instead it's just asking us to explain it.
    – Andrew
    Mar 27, 2017 at 14:30

1 Answer 1


It's implying that whenever the industry rose, an unexpected collapse happening in two years is common.

Industry rises by 100 %, then

  • Within a two-year time span from the rise, in 21 occasions out of 40, or 53 % of the time, there is a 40 % collapse.
  • In 19 occasions out of 40, or 47 percent of the time, there isn't a 40 % collapse.

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