Which is going to be the next Bear Factor?

Which is going to be the next Bear Factor?

The late 1980s bear market in the world Stock Markets were fuelled by the Gulf war and failure of East Asian Economies like Malaysia, Singapore, Hong Kong and etc. The bear market sustained till 1998.
The early 2000s bear market was fuelled by the dotcom bubble burst and also by the terrorist attack on WTC in USA. Then it terminated only on 2003.
The 2008 bear market was fuelled by real estate bubble, which impacted heavily the USA and also the World Economies. Since then it has pared some of it losses but still vulnerable for another bear attack.
If so, then which is going to be the biggest factor for the next bear market. May be it is real estate itself. As I believe the real impact of the real estate bubble is yet to be felt.
Another possible factor could be a Gold asset Bubble. Peaking Gold prices would lead to Bubble in days to come.
Let us wait and see…