Current decisions are made on expectations of what happens in the future, not on what actually happens in the future. Expectations may change immediately based

Current decisions are made on expectations of what happens in the future, not on what actually happens in the future. Expectations may change immediately based on the flimsiest of reasons. Here it could be the preception of change in government policy. Also 'all else being same' assumptions are just an explanatory tools for showing effect of basic economic principles (like supply/demand) within economy, not something to be taken too rigidly. There's no such thing as 'all else being same' in reality.