Stock traders on the floor of the New York Stock Exchange.Michael M. Santiago | Getty Images News | Getty ImagesMany large U.S. companies have seen their stocks swell since the presidential election.The top 10 performing stocks in the S&P 500 index saw returns of 18% or more since Election Day, according to data provided by S&P Global Market Intelligence, which analyzed returns based on closing prices from Nov. 5 to Nov. 20.[embedded content]Two companies — Axon Enterprise (AXON), which provides law-enforcement technology, and Tesla (TSLA), the electric-vehicle maker led by Elon Musk, an advisor to President-elect Donald Trump — saw their stocks gain more than 35%, according to S&P Global Market Intelligence.By contrast, the S&P 500 gained about 2% over the same period.’Usually a bad idea’ to buy on short-term gainInvestors should be cautious about buying individual stocks based on short-term boosts, said Jeremy Goldberg, a certified financial planner, portfolio manager and research analyst at Professional Advisory Services, Inc., which ranked No. 37 on CNBC’s annual Financial Advisor 100 list.”It’s usually a bad idea,” Goldberg said. “Momentum is a powerful force in the market, but relying solely on short-term price moves as an investment strategy is risky.”Investors should understand what’s driving the movement and whether the factors pushing up a stock price are sustainable, Goldberg said.Why did these stocks outperform?Lofty stock returns were partly driven by Trump administration policy stances expected to benefit certain companies and industries, investment experts said.Deregulation and a softer view toward mergers and acquisitions are two “key” themes driving bullish sentiment after Trump’s win, said Jacob Manoukian, head of U.S. investment strategy at J.P. Morgan Private Bank.Take the energy sector.Analysts expect the Trump administration will be more likely to greenlight oil and gas projects, for example.Trump has called for increasing fossil-fuel production and reversing Biden-era policies to cut U.S. greenhouse gas emissions. He picked Chris Wright, CEO of fracking company Liberty Energy, to head the Department of Energy.More from Personal Finance:The must-have gift of the season may be a ‘dupe’Could Trump reinstate the student debt Biden forgave?Most employees don’t use this ‘triple-tax-free’ accountEQT Corporation (EQT) — among the biggest U.S. natural gas producers — saw its stock surge 24% from Nov. 5 to Nov. 20, according to S&P Global Market Intelligence.It’s an example of a company that benefited from the “Trump momentum for energy,” Goldberg said.Relying solely on short-term price moves as an investment strategy is risky.Jeremy Goldbergportfolio manager and research analyst at Professional Advisory Services, Inc.Additionally, U.S. regulators will likely be much less stringent about allowing potential mergers during Trump’s second term, experts said.Companies in the streaming ecosystem — like Warner Bros. Discovery (WBD), which …
