(Bloomberg) -- The S&P 500 Index’s surprise 16% rally this year is rewarding traders who bought in early and punishing those who’ve remained skeptical. But fear of a downturn remains.Most Read from BloombergBoss of Failed Crypto Exchange Gets 11,000-Year SentenceIndia’s G-20 Win Shows US Learning How to Counter China’s RiseWall Street Fears a Too-Hot Economy as Recession Bets PlungeCalifornia Shows an Electric-Car Uprising Headed for the USEverything Apple Plans to Show on Sept. 12: iPhone 15, W