Shares of International Business Machines Corp. IBM, -0.85% dropped in Tuesday's extended session after the technology giant reported its revenue fell year-on-year for a 15th straight quarter. IBM said its fourth-quarter earnings fell to $4.46 billion, or $4.46 a share, from $5.48 billion, or $5.51 a share, a year earlier. Excluding charges and items, Big Blue would have earned $4.84 a share. Revenue shrank to $22.06 billion versus $24.11 billion. Analysts surveyed by FactSet had forecast earnings of $4.81 a share on revenue of $22.09 billion. IBM shares fell 1.7% in after-hours trading.