The following graph shows PR approvals for istio/istio since 2020.

DevA 100 <-> DevB 50 indicates DevB approved 100 PRs from DevA, and DevA approved 50 PRs from DevB.

The data was collected from our policy bot data and graphed using flourish:

gcloud spanner databases execute-sql main --instance istio-policy-bot --project istio-testing --format=json --sql='select prr.Author as Approver, pr.Author as Author, count(*)
from PullRequestReviews as prr
join PullRequests as pr on pr.PullRequestNumber = prr.PullRequestNumber
where SubmittedAt > "2020-01-01T00:00:00.00Z" and prr.state = "APPROVED" and prr.RepoName = "istio"
group by Approver, Author' \
| jq '.rows[] | select((.[2]|tonumber) > 5) |  .[1] + "," + .[0] + "," + .[2]' -r

If the dynamic graph doesn't work a static version can be found here.

2023 update

Data from Jan 1 2022 through Jan 25 2023: