From Chaganomics:

This data was edited to best fit the visual description. All data from OpenTable: State of the Industry. 

From OpenTable:

The data indexes two things. First, the overall impact of Covid 19 on the industry by showing year-over-year seated diners at a sample of restaurants on the OpenTable network across all channels: online reservations, phone reservations, and walk-ins. For year-over-year comparisons by day, we compare to the same day of the week from the same week in the previous year. For example, we’d compare Tuesday of week 11 in 2020 to Tuesday of week 11 in 2019. Only states or metros with 50+ restaurants on the OpenTable network for 2019 or 2020 are included in the sample. To better reflect the state of the industry overall, this dataset is based on a sample of approximately 20,000 restaurants that provide OpenTable with information on all of their inventory. This sample of restaurants typically accounts for a majority of our seated online reservations. Second, a comparison of year-over-year seated covers to demonstrate where we are seeing recovery start to take shape. This table shows year-over-year seated covers across all channels at only the restaurants that have chosen to reopen in a given market. As an example, if there were 50 seated covers in restaurants that have recently reopened in a given locale on May 11, 2019 and on the same day in 2020 there was 1, then 2% will be displayed. For this chart, only markets with 500+ restaurants on OpenTable of which 10%+ are accepting online reservations are included. - See Data @ OpenTable