Physical evidence you say? Go to your gameshop, or any gameshop and compare the overall sizes of the displays for each system. A dying console has a much smaller display rack than the popular one.
However a new console begins with a smaller segment for it's only building it's games library, as it continues to become popular the displays for that console will grow. That being said you have to wait atleast 1 year after the release to have a better vision. Once a display will reduce in size, it will almost be impossible to turn the tide.