Even in the past when printed phone books were common, the number of pages would have varied depending on:
* The year: The number of listings changed over time.
* The publisher: Different publishers might have included more or fewer listings.
* The type of phone book: There were likely separate books for residential, business, and government listings.
If you're curious about a specific phone book from the past, you might be able to find information about it online or at a local library.