"It's hard to quantify the exact degree of how much [a lack of used-vehicle inventory] impacted our sales other than it had an impact on our sales," Nash said.
He said CarMax was still light on inventory at the end of August but returned to a solid position in September.
CarMax sold 217,330 used vehicles in the quarter, up 3.9 percent in total and up 1.2 percent on a same-store basis. Company revenue rose 3.3 percent to $5.37 billion while net earnings soared 27 percent to $296.7 million.
Ali Faghri, managing director at Guggenheim Securities, said in an email that while CarMax's results were good — above analysts' consensus — some investors may have been disappointed given the strong used-vehicle sales and profits reported by competitors.
Investors also are looking for more key performance indicators on the omnichannel strategy as it "is a big strategic focus for the company and important to the long-term growth story (especially as COVID has clearly accelerated the shift to online buying)," Faghri wrote.
Sharon Zackfia, a partner at William Blair, said in a research note last week that some investors have fretted that CarMax is losing ground to competitors with more impressive sales gains.
But this doesn't hold up to scrutiny, she said. The research firm's Web data analysis shows CarMax is at least keeping pace with, if not exceeding, market share gains by key rival and online used-vehicle retailer Carvana.
CarMax sold at least 19,200 more vehicles in July, August and the first few weeks of September vs. the same period a year earlier while Carvana sold 18,100 more vehicles during that period, she said.
Zackfia added: "This supports our thesis that CarMax can thrive and gain share even as digital disruptions occur given the massive, fragmented nature of the used car industry."