Don't know how old this article is and if it's common knowledge, but it seems that repair kits are replacing the spare tyre. Their reasoning is that what you might end up paying for a replacement tyre if you fail with the repair kit is compensated by a lighter car giving additional fuel economy. Sure 
http://www.bbc.co.uk/programmes/b006mg74/features/spare-tyre

http://www.bbc.co.uk/programmes/b006mg74/features/spare-tyre