Reuters / Rafael Marchante Well, it was a fun ride while it lasted. Red-hot corporate earnings growth — historically the biggest contributor to share-price appreciation — has nowhere to go but down, Strategas Research Partners says. This is significant because any sort of slowdown would deprive the market of its most crucial driver — one that has helped keep the stock market afloat amid middling economic data and elevated geopolitical risk. A big part of Strategas' argument stems from the fact that the period against which current earnings are compared — the first half of 2016 — was notably weak.