Better-than-expected earnings reports have powered the S&P 500 to what is currently a 9% gain on the year. 

"We're at right about half time for this earnings season and the picture is anything but clear," said Mike Loewengart, vice president of investment strategy at E*Trade. "We've enjoyed a heck of a rally so far this year, but that can easily be disrupted if more companies miss the mark on earnings," he added, noting that there could still be a number of companies missing expectations and seeing price target cuts from analysts.

Four big companies could provide a little added clarity to the picture Thursday.  

Twitter

Twitter Inc. (TWTR - Get Report) will report fourth-quarter earnings before the opening bell Thursday. Wall Street is looking for adjusted earnings-per-share of 25 cents on revenue of $867 million. Twitter peers Snap Inc. (SNAP - Get Report) and Facebook Inc. (FB - Get Report) both beat analysts estimates on revenue and EPS, although Snap's beat was attributable to better-than-expected user additions, as the company was able to fix a long-burdensome bug on the Android version of the app. 

T-Mobile

T-Mobile U.S. Inc. (TMUS - Get Report) reports fourth-quarter earnings before the opening bell Thursday. Analysts are expecting adjusted EPS of 69 cents on revenue of $11.4 billion. 

Fiat Chrysler

Fiat Chrysler Automobiles NV (FCAU - Get Report) will report fourth-quarter earnings before the market opens Thursday. Adjusted EPS is expected to be 62 cents on revenue of $34.12 billion. General Motors Co. (GM - Get Report) , a major peer to Fiat, beat earnings expectations and reiterated full-year 2019 guidance Wednesday morning, on the back of strong U.S. sales, while global sales were weaker. 

Dunkin' Brands

Dunkin' Brands Group Inc. (DNKN - Get Report) will report fourth-quarter earnings before the market opens Thursday. Analysts are expecting adjusted EPS of 61 cents, which would be a 4% year-over-year decline, and GAAP EPS of 57 cents, which would be a 73% decline. Revenue is expected to be $329.88 million. Starbucks Corp. (SBUX - Get Report) handily beat revenue and earnings estimates in late January on the back of a strong U.S. sales quarter. Some sales checks done by analysts are suggesting upside.

"Checks suggest optimism around the business and direction of the brand under new CEO Dave Hoffmann," wrote Cowen & Co. analyst Andrew Charles. Dunkin' is trying to re-establish its brand as a go-to coffee and food chain for hurried customers who need speed. 

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