Once the humble domestic ass carried people and their possessions throughout the world. But that was before the invention of the donkey, and ever since then ass usage has been sagging.
2006 was a particularly bad year for the ass - 'rock bottom' in the words of one commentator. In Bombay, the world's largest ass trading market had to close because not enough ass was on display for punters to be able to choose which one to buy. As a result there is now an ass gap in trade between India and Brazil. The Brazilians are one of the world's major investors in ass.
Traders predict that the gap in trade could become so large as to form an 'ass hole' in the market, and unless something else big like the horse comes along to fill that ass hole, nobody's walking anywhere.
One possibility would be to use inflation to artificially pump up the ass market. This would allow the rump of asses to survive, without shaking the ass business too much. It would however had the unfortunate side effect of wedging some manufacturers out of the market. But as many analysts have said, if you're looking for shit you can always take it in the ass industry.