Who started world war 1?

Not really anyone, but it started because someone from Germany killed Archduke Franz Ferdinand of Austria.

Serbia.

Explanation:

The immediate cause for World War 1 was the assassination of the Archduke Franz Ferdinand of Austria and his pregnant wife Sophie. Archduke Franz Ferdinand of Austria was the nephew of Emperor Franz Josef and heir to the throne of Austria and Hungary. The assassination was planned by a Serbian terrorist group, called The Black Hand and the man who shot Franz Ferdinand and his wife was a Bosnian revolutionary named Gavrilo Princip.

by creating a labor shortage that pushed the continent toward a market economy