NEW YORK (TheStreet) -- Costco (COST) shares were trading lower premarket after the retail giant reported second-quarter profit 15% lower than a year earlier.

Before the bell, the stock had taken off 2.9% to $113.09.

In the three months to mid-February, the membership-only retailer posted net income of $463 million compared to the year-ago quarter's $547 million, even as revenue jumped 5.8% to $26.31 billion.

Earnings of $1.05 a share missed consensus by 12 cents, according to analysts surveyed by Thomson Reuters.

Though last year's profits were boosted by a $62 million tax benefit, the company said the results were not ideal.

"The year-over-year comparison was unfavorable," said chief financial officer Richard Galanti. "The first four-week period of the quarter represented the majority of earnings underperformance in the quarter."

Costco's second quarter began on Nov. 25, a period when retailers were offering steep discounts amid an aggressively promotional environment, a factor of worse-than-expected winter storms and six less shopping days between Thanksgiving and Christmas.

The Issaquah, Washington-based company said lower earnings were attributable to weaker sales and gross margins in its non-foods categories, weaker margins in its fresh food segment, and lower international profits due to unfavorable forex rates. Overall, gross margins were clipped to 11.26% from 12.48% in the year-ago quarter.

Comparable sales increased 3% over the quarter, with 4% growth in the U.S. and remained unchanged internationally.

Margin pressure is being felt across the industry. The world's largest retailer, Wal-Mart (WMT), recently reported a 21% drop in net profits over its January-ended quarter, blaming wintery weather and a reduction in the government's food-stamp program for diminished earnings.

WATCH: Hidden Camera Captures Debate Over Costco's Future

If you liked this article you might like

Cramer: How to Avoid Being Amazon Roadkill

How to Invest Like Billionaire Warren Buffett

How to Live Just Like Billionaire Warren Buffett

5 Stores With the Best Return Policies

Analysts Wrong on iPhone; Retail Not Going Away: Best of Cramer