Shares of Western Digital ( WDC) were down in after-hours trading Thursday after the company said fourth-quarter earnings slipped 5% as distribution pricing hurt margins.The Lake Forest, Calif.-based hard drive producer said earnings fell to $29.6 million, or 14 cents a share, down from $31 million, or 15 cents a share, in the same period last year. Sales rose 10% to $748.8 million from $680.3 million, driven by a 19% increase in units shipped, to 12.5 million from 10.5 million. Analysts had forecast earnings of 14 cents a share on revenue of $704.6 million. The company indicated that fourth-quarter pricing in the distribution channel was very aggressive and that it experienced a higher mix of business with OEM customers, which is typically a lower gross margin business than distribution. These factors resulted in lower total gross margins of 13.5%. Shares of Western Digital were down more than 6% in after-hours trading after closing the regular session up 32 cents, or 4.1%, to $8.23.