1: https://www.npr.org/templates/transcript/transcript.php?stor...
It also points towards the ability of other companies to compete with Walmart in niche areas (at least niche compared to Walmart). I could see a future where a few chains each carve out a chunk of the more popular Walmart inventory and out-compete Walmart on physical location, as Dollar General has done.
You can kind of imagine them as CPU cache layers. In-town local stores are L1 cache with great speed but relatively poor choice for all but the most common items, Walmart is L2 cache with good speed (not still slower for most, as it's a ways away for the majority of people) and better selection, and the internet is general memory with everything you might need, but slow speed. There has been a major upheaval in the L! level because of both a major shift in how close/fast and large L2 got (a shift from major cities to large complexes in rural areas) and a huge boost in general access (the internet), but I don't think it's all played out yet, since I think there's still need at the local level that's not fulfilled well anymore.
Sorry for the tortured analogy, but it did probably save time on both ends.