Friday is the unofficial start of the quarterly earnings season, with three major U.S. banks - JPMorgan Chase, Citigroup and Wells Fargo - announcing their results before rock bottom. BlackRock, the world's largest asset manager, and State Street, the trustee bank, will also report later in the day. The Dow and S&P 500 ended the week lower, as higher-than-expected inflation data this week led to turbulence, with traders less enthusiastic about a rate cut from the U.S. Federal Reserve, while the tech-dominated Nasdaq was on track to post its first gain in three weeks this week.