Shares of Union Pacific Corp. UNP shed 1.0% in premarket trading Tuesday, after the railroad operator reported fourth-quarter profit and revenue that came up shy of Wall Street expectations, as continued challenges in hiring, inflation and extreme winter weather were weighed against growth in carloads. Net income fell to $1.64 billion, or $2.67 a share, from $1.71 billion, or $2.66 a share, in the year-ago period, as the number of shares outstanding was reduced by 4.4%. The Fact Set consensus for earnings per share was $2.77. Revenue grew 7.8% to $6.18 billion but was below the FactSet consensus of $6.28 billion. Operating…