It's a quick way to reference the impact of a disaster or pandemic, by looking at the closure of specific stores. Waffle House locations are notable indicators of the aftermath of a hurricane, and more recently Apple Stores are an indicator of the pandemic response.

The Waffle House Index

The Waffle House Index is an informal metric [...] used by the Federal Emergency Management Agency (FEMA) to determine the effect of a storm and the likely scale of assistance required for disaster recovery.

Wikipedia

During the COVID-19 pandemic, @jcenters proposed an Apple Store Index, since Apple inherently has a monetary incentive to keep stores open, but only when it's safe.

The "Apple Store Index" says it's not yet time to reopen the economy

Apple had originally planned to keep stores closed until March 27, 2020 but they have since been closed indefinitely. [...] It’s hard to overemphasize what a drastic action this was by Apple to protect employees and customers.

The Prepared | Apr 21 | Josh Centers

The map currently defaults to Apple Stores, but you can toggle it to include Waffle House locations. This is largely US-centric, and especially Southern US focused with Waffle House. If you have ideas for other stores that might be good indicators of disaster/pandemic impact, let us know!