Stocks gained steam in the first half of 2017 thanks to strong earnings and one expert expects a similar boost in the current reporting season.

Brad McMillan, chief investment officer at Commonwealth Financial Network, uses banking earnings as a barometer for the rest of the season and said that even tough bond trading performance was lackluster for Goldman Sachs (GS - Get Report) , Morgan Stanley (MS - Get Report) and Citigroup (C - Get Report) , their underlying businesses are strong. 

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