Often this happens because book collectors judge minor defects in an old book so harshly as to make them seemingly unsaleable. This widespread practice probably peaked in the 1970s or 1980s, because the price for old engravings and especially for old maps was outstripping that of rare books. However—in part because so many rare, illustrated books were "broken" in this manner—the price of the intact books has now risen the point where an old book is typically worth more intact.