When Amazon.com, Inc. (NASDAQ:AMZN) reports second-quarter earnings after the closing bell Thursday, investors will be looking for an improvement in the company’s narrow profit margins.

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Analysts expect the Seattle-based online retailer to report $15.74 billion in sales, which would represent a 23% jump from a year earlier. Net income is likely to be $28.3 million, a four-fold increase from last year, according to analysts’ estimates.

Despite operating margins that have been less than 1% in recent quarters, Amazon.com, Inc. (NASDAQ:AMZN) shares have jumped 20% this year.

Amazon 2Q13 expectations

Aaron Kessler of Raymond James estimates 2Q net sales of $15.81 billion, slightly above the consensus of $15.74 billion and in line with guidance of $14.5-16.2 billion. The analysts estimate 26% y/y North American sales growth  and 25% y/y for ex-neutral international growth. Analysts also project an stimated non-GAAP operating income of $371 million vs. guidance of $350 million and consensus of $368 million and a non-GAAP operating margin of 2.3% vs. 2.8% last year. Non-GAAP EPS is expected to be $0.45, below the consensus of $0.59.

Amazon eCommerce data points mostly stable

According to ChannelAdvisor, 2Q Amazon.com, Inc. (NASDAQ:AMZN) same-store sales increased 29.0% y/y, a slight deceleration from 32.2% y/y in 1Q. Additionally, according to Mercent, an online marketing technology company, Amazon’s SSS growth across its platform has increased to 25% y/y in 2Q, a slight acceleration from 22% y/y in 1Q  but down from 33% y/y in 2Q12. For 2Q, Raymond James estimates an Amazon revenue growth for U.S. Electronics & Other General Merchandise  of 28.0% y/y vs. 28.0% y/y in 1Q.

Amazon comScore data mostly positive

U.S. PC comScore data (excluding mobile) indicates unique visitors increased 9% y/y (vs. +8% y/y in 1Q) and total visits decelerated to 16% y/y. For Europe, 2Q comScore data (through May) indicate a 10% y/y increase in unique visitors  and a 30% y/y increase in total visits.

Amazon key questions in Q213 earnings report

Raymond James believes investors would like to see unit growth stabilize near 30% in the near term and expects continued margin improvement driven by 3P shift, AWS update, Outlook for 2013 fulfillment center expansion, international investment spending and grocery roll out plans.

Amazon.com, Inc. (NASDAQ:AMZN) has spent heavily to build out new distribution centers closer to urban centers, as well as on developing new technology like its Kindle Fire tablet computers, and content acquisition for its streaming movie business. In this year’s first quarter, Amazon boosted such spending by 22% to $15.9 billion, virtually wiping out its $16.07 billion in sales.

Amazon has been working to keep pace with Netflix, Inc. (NASDAQ:NFLX) in offering streaming content such as movies and television shows. It signed a multi-year deal with Viacom, for instance, for thousands of new shows.