See CMS 6.103–6.110 for a discussion of the slash. Use slashes for ratios and other numerical relationships, for some abbreviations, and to indicate that a person or thing has two functions.
Examples: P/E, 50/50, 60/40 asset mix, c/o, broker/dealer, and/or
The correct use of the acronym “P/E” is without the word “ratio,” which is implied by the use of the slash. To avoid over-hyphenation, you might use “the ratio of price to earnings” or “price/earnings” (without “ratio”) rather than “price-to-earnings ratio.” Handle similar phrases similarly; for example, use “the ratio of price to book value (P/BV),” after which you may use “P/BV” without the word “ratio.”