WASHINGTON — Inflation is widely reviled as a kind of tax on modern life, but as Federal Reserve policy makers prepare to meet this week, there is growing concern inside and outside the Fed that inflation is not rising fast enough. Some economists say more inflation is just what the American economy needs to escape from a half-decade of sluggish growth and high unemployment. The Fed has worked for decades to suppress inflation, but economists, including Janet Yellen, President Obama’s nominee to lead the Fed starting next year, have long argued that a little inflation is particularly valuable when the...