Investors knew Kroger (NYSE:KR) would post a strong sales figure for its fiscal first quarter, a period that covered maximum social distancing efforts in the U.S. But the scale of that revenue spike was still shocking.

The supermarket chain said on Thursday morning that comparable-store sales jumped 19% in the three-month period that ended on May 23. That result blew past the 2% uptick that shareholders had been used to seeing from Kroger in recent quarters. It also suggested market share gains against rivals like Walmart (NYSE:WMT), which boosted comps by 10% in its latest quarter. Those numbers aren't directly comparable, though, since Walmart's first quarter ended on April 30 and consumer demand for home essentials is shifting by the week.

A grocery store employee stocks fresh vegetables.

Image source: Getty Images.

Still, Kroger's management team has seen enough data to feel confident that they'll surpass their initial goal of at least 2.25% sales gains for the full fiscal year. It seems likely that the final result will be below the latest 19% surge, but the chain's actual performance will depend on unpredictable factors including economic growth trends and the path that the novel coronavirus takes through the summer and fall months.

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