has a well-earned reputation for generosity in years that most resemble 2017, december has produced furse gains of around 2% on average. december has never once been the weakest month of any year. which is encouraging given the worst 2017 was march when the market was down less than a 0.1%. it still makes sense to expect a less smooth ride for stocks, even if the bull market carries higher still. the tax cut will produce relative winners and loser, and th on a humming economy could have unintended effects on interest rates and inflation. if the market does grow choppy in the coming weeks and months, there's a bright sign for investors. after such a long calm rally as we've had this year, the first sharp pullback is rarely the start of a lasti that's what the history books tell us. i'm mike san tolli at the to new york market exchange sploo cvs has agreed to buy aetna, bringing two big health care .akers in the bi today shares of both stocks were lower. the combined company is widely expected to transform. bertha coombs explains. >> cvs and aetna's ceos say they have tried to offer better