The big headline number out of Costco's (NASDAQ:COST) latest earnings release was 15%. That's the rate at which the warehouse giant improved its comparable-store sales from last year, after excluding shifts like gasoline price and exchange rate swings.

That increase reflected one of the strongest consumer spending environments in years, but it only told part of the earnings story. Let's look at a few other metrics investors might have missed from the report.

A man shopping at a bulk warehouse.

Image source: Getty Images.

1. Renewal rate: 91%

Nearly everyone who had an invitation to let their membership lapse chose instead to pay up for another year. Costco's subscription renewal rate was 91% this quarter, keeping it at the near-record level that it has been at for over a year.

That's great news for the business because it implies that shoppers are getting plenty of value from their memberships even as more spending shifts online. Costco is competing aggressively in this arena, too, including with a big push into oversized product deliveries this past year.

The strong renewal rate also lifts earnings, with membership income rising to $900 million from $815 million a year ago. That accounts for over half of Costco's operating earnings.

2. Inflation: 3%

In early March, Costco executives estimated that overall inflation across most consumer categories was running at between 1% and 1.5%. But a lot has changed since then, with prices rising thanks to transportation delays and supply challenges on things like beef, semiconductor chips, and oils. Now inflation appears to be running in the 2.5% to 3.5% range. "The inflation pressures abound," CFO Richard Galanti said in a conference call.

Costco is using its clout in the industry to minimize the effect on shoppers through strategies like front-loading orders. Yet prices are still creeping up as costs rise on everything from aluminum to plastic, pulp, freight, and commodities. That inflationary environment favors Costco, given its price leadership status in the industry.

3. Customer traffic growth: 12%

Digital sales jumped 38% this quarter, and Costco credited strong demand across consumer discretionary categories like jewelry and home furnishings, plus higher volumes in its bulky delivery platform. That push is adding room to begin competing against leaders like Wayfair and Home Depot now that delivery times are dropping.

But shoppers still flooded Costco's retailing warehouses, with traffic rising by double digits again this quarter. The big boost came from its non-food aisles that tend to carry higher profit margins. The fresh food niche contracted slightly but was still high by historical standards.

Rising membership fees ahead

Galanti fielded a few questions in the conference call about when Costco might be raising its membership prices, which immediately jolts earnings growth. It has been about four years since the last increase, and the company tends to increase fees every five years or so.

The strong customer traffic and renewal rates imply Costco wouldn't struggle to pass along another fee hike, especially as members are getting more benefits from faster home delivery across a wider range of products. As for the exact timing of a boost, "We'll have to wait and see," Galanti said, "but we certainly feel good about our competitive position."

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