U.S. stocks ended 2018 skimming  bear market territory . In the new year, the market has bounced back somewhat but remains volatile. This week,  Wharton finance professor Jeremy Siegel   joined the  Knowledge at Wharton show on SiriusXM  to discuss the market outlook, Fed rate hikes and the impact of the U.S.-China trade war. He is also co-host of the show “ Behind the Markets ” on Wharton Business Radio every Friday. Siegel  was joined by  Gad Allon, who is director of the Jerome Fisher Program in Management and Technology at Wharton and also professor of operations, information and decisions.  An edited transcript of the conversation follows. Knowledge at Wharton : As we continue our 2019 look-ahead series we are going to focus on the markets, which have been on a rollercoaster ride the last few months. The Dow Jones Industrial Average ended up seeing a decline of more than 10% last year. Both the Nasdaq and the S&P 500 saw declines as well.…