Barron's STOCKS TO WATCH The Biggest Loser: Helmerich & Payne Slumps 5.5% Tumbling crude prices sunk oil-services stocks and made Helmerich & Payne the worst performing stock in the S&P 500. By Ben Levisohn July 21, 2017 5:39 p.m. ET Helmerich & Payne(HP) tumbled to the bottom of theS&P 500today as oil prices fell, sinking oil-services stocks. ILLUSTRATION:GETTY IMAGES Helmerich & Payne dropped 5.5% to $54.13 today, while the S&P 500. TheVanEck Vectors Oil Services ETF(OIH) fell 2.5% to $25.02 as oil dropped 2.5% to $45.77 a barrel today. Oil services stocks fell despitestrong earnings fromSchlumberger(SLB), which declined 0.7% to $66.53. Helmerich & Payne's market capitalization fell to $5.9 billion today from $6.2 billion yesterday. It reported a net loss of $55 million on sales of $1.6 billion in 2016.