As the old saying goes, a picture is worth a thousand words.
That being said, here is a picture of the S&P 500 (yellow line) and the US Gross Domestic Product (GDP) on an annual bar chart basis. The short horizontal red line is the GDP for 2016 which matches the GDP for 2011, both at a paltry 1.6%.
Not much to say here other than, something has to give. One can only stretch an elastic band so far before it snaps.
Either GDP rises towards the 4% range (noted by the red arrow upwards) or the S&P 500 needs to drop (noted by the yellow arrow downwards), or a combination of the two, in fact.
Not much else to say.