Analysis of information sources in references of the Wikipedia article "Apostrophe" in English language version.
The only statistical investigation of the genitive case that we are aware of can be found in Fries 1940. Fries found that the possessive genitive was the most common, but that it accounted for only 40 percent of all genitives.
Letters are usually pluralized with 's: mind your p's and q's although capital letters are sometimes pluralized with s alone. The use of 's to form the plurals of numerals, abbreviations, and symbols is not now as common as pluralization with simple s; 1970s, CPUs, &s are more likely to be found than the apostrophied counterparts.
Guidance:...Word messages should not contain periods, apostrophes, question marks, ampersands, or other punctuation or characters that are not letters, numerals, or hyphens unless necessary to avoid confusion.
this is the preferred character to use for apostrophe
