The article "Two Theories of Money Supply Endogeneity: Some Empirical Evidence" explores different ideas about how the amount of money in circulation is determined. The researchers looked at real-world data to see which theory best explains how money supply changes over time. They found that one theory, called the "horizontalist" view, aligns better with the actual behavior of money supply compared to the traditional theory. This suggests that the way money is created and controlled might be different than what was previously thought.