Why do people euthanise their pets?

Yesterday I promised to caugh up the answer, so here it is. Jeff, was on the right track regarding the dogs. About half af the dog euthanasias are because of old age or disease. But a disturbing finding is that almost every fourth dog (23%) is euthanised because of behavioral problems! These are treatable in most cases, but need work. The cats are a different story, according to my research only a quarter is euthanised because of disease or old age. Convenience reasons (we are moving, taking a long vacation, someone developed allergies (I suspect this is often given as an "excuse" because people can´t deal with the responsibility of having a pet)) are 35% of the reasons given, another 17% is behavioral problems (this was a big surprise for me, I thought these were much less common in cats), and 15% is trauma (usually run over by car or fell down from window). These findings are consistant with the few studies that have been made on this issue, in Denmark, Scotland and Canada.