The New York Times Manual of Style and Usage (1999) agrees with Words into Type about the apostrophe, although about little else:
decades should usually be given in numerals: the 1990’s; the mid-1970’s; the 90’s. But when a decade begins a sentence it must be spelled out. [example omitted]; often that is reason enough to recast the sentence.
NY Times seems pretty reputable and they like the grocers’ apostrophe, your example is some random person’s summary
Many style manuals allow referring to decades with apostrophes before the s, and no apostrophes before the abbreviated year
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I can give you a stack exchange: https://english.stackexchange.com/questions/13631/is-an-apostrophe-with-a-decade-e-g-1920-s-generally-considered-incorrect
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Too also quote:
NY Times seems pretty reputable and they like the grocers’ apostrophe, your example is some random person’s summary