How to retrieve exact reputation on "legendary day"?

Question

Some weeks ago I asked about the most legendary users on the network. Now that my name shows up in that list as well (or will show up when the SEDE data is updated) - a comment of another user triggered this thought:

Is there an easy way to compute the reputation that "legendary badge" holders had ... on that day, when the badge was awarded?

( and yes, this is totally pointless, but still I am curious if that would result in a "ranking" where I maybe show up in the overall top 10 or so )

Answer 1

On the SEDE, we can see the reputation of a given user on its last synchronization time (typically late weekend), and we can also see the time as he got his legendary badge.

However, we can't get the exact reputation in that given time, because the SEDE doesn't show us that. It also doesn't contain all the required information, from which we could calculate it. But, most of the events affecting the reputation are available in the SEDE. These are:

1. votes (up, down)
2. accepted answers
3. cases as the user accepts an answer
4. bounties
5. association bonus (except rare cases)
6. +2 for edited posts for users with lesser as 2000 rep

The SEDE doesn't show us:

7. -1 reputation loss by downvoting an answer
8. sometimes posts are deleted on a way that the reputation gained/lost by them remains
9. -100 reputation losses for offensive/spam flags
10. Also we practically can't calculate the effect, that the reputation is minimized in 1, thus, for example, a rep 1 user with a voted down post doesn't go to -1.

The second group, although it can affect reputation, but these are typically rare. Thus, a good estimation of the reputation in a given time is reachable.

The majority of the reputation gained by legendary users is coming from (1) and (2). I wrote a simple query what does an estimation using it. You can parametrize it with the time you want to get, and with the id of the given user (you can see that from the link of his profile page). The format of the required date is like 2017-07-28 (thus, year-month-day).

Here it is.

To me, it estimates 5059 rep on the StackOverflow for today, while my real reputation is roughly 4600. The difference is coming from answer downs and from bounties.

If you find it interesting, I am open to extend/tune it.

Answer 2

SEDE doesn't record historical reputation (or votes), just the state at the time the data is exported. You could get an approximation by digging through the data dumps (published a few times a year) and/or specific users' reputation-history pages, but that sounds labor-intensive.

You could capture new cases of Legendary each week when SEDE is updated and then save those results locally. (SEDE can export query results as CSV.) This would give you data that you could compare over time.

Answer 3

Here is a SEDE query which attempts to list reputation on 'Legendary Day' for all users who have the badge. It runs faster than I expected on this site, but we only have 15 Legendary users here:

# User                        Legendary Day          Rep
----------------------------------------------------------
1 Jeff Atwood                 2010-03-23 13:17:31    51306
2 Pekka supports GoFundMonica 2013-12-13 00:00:00    72125
3 Manishearth                 2019-11-14 04:20:11    75204
4 Oded                        2014-07-23 00:00:00    80544

Stack Overflow is too big for it to work; here is a version which works for a single user.