Parents also enjoy the company and the social interaction and try to maintain the relationship. Many parents want to protect their children and offer them the best possible start in life. The parents, for their part, often enjoy living with their children. Many children wish to live with their parents until they marry. This situation allows the children to live in considerable comfort, and while many save money, others spend all their income on luxury items, traveling, and other non-essential expenses. This is a traditional Japanese living arrangement, though its prevalence has decreased in recent years. However, this situation occurs less frequently and the term parasite couples is less well known. Professor Yamada subsequently coined the related term parasite couple to refer to married children living with the parents of one partner. The catchy phrase quickly found its way into the media and is now a well-known expression in Japan. The expression parasaito shinguru was first used by Professor Masahiro Yamada of Tokyo Gakugei University in his bestselling book The Age of Parasite Singles ( パラサイトシングルの時代, parasaito shinguru no jidai), published in October 1999.