Ed Yardeni, president of Yardeni Research, has predicted the economy will "roar" through the 2020s and perhaps into the 2030s, propelled by productivity growth. It's a bullish recipe for markets, too. Barron's Senior Managing Editor Lauren R. Rublin and Deputy Editor Ben Levisohn talk with Yardeni about his Roaring 20s thesis, and his 2025 market outlook.