The stock market could experience a correction soon. Prices already reflect a wallop of government spending and central-bank aid that can’t get much larger from here, Bank of America warns. Other market watchers are downbeat as well. The S&P 500 entered Friday up about 1% year to date, but ended the day with a loss of 0.7%, bringing the year-to-date move to 0.3%. Stocks were down even after President-elect Joe Biden said he wants to spend an additional $1.9 trillion to tide over consumers and businesses until normality returns. Meanwhile, valuations are high. The equity risk premium—the earnings yield on the average