Stocks have been volatile in recent weeks, but after a strong gain on Monday, the major equity indices were indicated to have a strong open on Tuesday as well. The current bull market may now be over nine years old, but the trend of buying pullbacks is still more vulnerable to sellers, volatility and each major news headline than in 2017. Many investors are finding it hard to decide how they want their assets positioned for the rest of 2018 and beyond.

24/7 Wall St. reviews dozens of analyst research reports each day of the week. Our goal is to find new ideas for investors and traders alike. Some analyst reports cover stocks to buy, and some cover stocks to sell or to avoid.

Additional color and commentary has been added on most of the daily analyst reports. The consensus analyst price targets and other valuation metrics are from the Thomson Reuters sell-side research service.

These were the top analyst upgrades, downgrades and other research calls from Tuesday, April 17, 2018.

ABB Ltd. (NYSE: ABB) was raised to Neutral from Sell at UBS.

Acacia Communications Inc. (NASDAQ: ACIA) was down about 36% at $25.63 on Monday after an announcement about the Commerce Department banning American companies from selling, exporting or re-exporting components, software and technology to Chinese telecom equipment maker ZTE. Piper Jaffray downgraded Acacia to Neutral from Overweight.

Antero Resources Corp. (NYSE: AR) was downgraded to Neutral from Buy with a $22 price target (versus a $20.62 prior close) at Citigroup.

Bristol-Myers Squibb Co. (NYSE: BMY) was downgraded to Equal Weight from Overweight with a $58 price target (versus a $54.08 close) at Morgan Stanley.

Cabot Oil & Gas Corp. (NYSE: COG) was downgraded to Neutral from Buy with a $25 price target (versus a $23.96 close) at Citigroup.

Chesapeake Energy Corp. (NYSE: CHK) was downgraded to Sell from Neutral with a $2 price target (versus a $3.11 close) at Citigroup.

Coca-Cola Co. (NYSE: KO) was raised to Neutral from Sell with a $46 price target at Goldman Sachs.

Dropbox Inc. (NASDAQ: DBX) has seen its underwriters post-IPO quiet period come to an end. The shares closed down almost 3.3% at $29.02 on Monday, and they have a post-IPO trading range of $27.75 to $34.83. 24/7 Wall St. has set a full list of analyst calls in an expanded piece due to the raw number of calls. It was a mixed view, with calls from Canaccord Genuity, JPMorgan, JMP Securities, Goldman Sachs and many more. Dropbox shares were last seen up 2.5% at $29.75 in early trading indications on Tuesday.

GrubHub Inc. (NYSE: GRUB) was started as Overweight and the price target was raised to $120 at Stephens.

International Paper Co. (NYSE: IP) was downgraded to Sector Perform from Outperform with a $57 price target (versus a $53.75 close) at RBC Capital Markets.

Koninklijke Philips N.V. (NYSE: PHG) was raised to Buy from Hold at Deutsche Bank.

Merck & Co. Inc. (NYSE: MRK) was raised to Overweight from Equal Weight at Morgan Stanley. Merck’s expanded lung cancer news helped shares close up 2.6% at $58.65 on Monday, and the stock was indicated up 1.9% at $59.80 on Tuesday.

Molson Coors Brewing Co. (NYSE: TAP) was downgraded to Neutral from Buy with an $83 price target (versus a $73.55 close) at Goldman Sachs.

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