They have other pillars in Haikyuu and Heroaca. Its a gross oversimplification to say OP is single-handedly keeping the magazine afloat because there are lots of people that don't even read OP weekly. I've seen guys who just tear out the Yuragi pages and throw the rest away. I've also seen people that read Jump simply for Kochikame or are reading it right now for Heroaca, Haikyuu or, ironically, Spring Weapon. There is no empirical evidence to suggest that OP is the only thing holding up Jump though I agree that once it ends Jump's print numbers and possibly readership will dramatically fall. Kids nowadays can't even get into OP unless they read it with Jump+ and that's at chapter 179 right now. There are always the pirate sites like the recent mangamura which seems to be picking up with kids but that's a whole different issue. Jump's brand is big enough to hold itself up.
I wouldn't call Haikyuu!! a pillar at all. Neither MHA, even if I'm a big fan of the series. They are both big series, absolutely. Being pillars is definitely a stretch and you can see it in the way WSJ does the combined issues. Unlike in the past, where you could clearly see WSJ had 2-3 mainstay series they relied on (Naruto, Bleach, Toriko, even Assassination Classroom despite it being short, it was still a smash hit right away and got numbers 99% series never do), you can clearly see now that OP is the main one series they trust right now. In addition, OP volume sales stand at 3 to 3.5 million. Even if we consider just a third of those who read OP are from WSJ, that's still a million readers. Numbers wise, OP is the only thing keeping the magazine from falling face first just like how SNK is the only thing keeping Bessatsu from being stopped.
If this was in respect to Weekly Young Jump where you have 3 series all selling similar to each other and all mostly similar in popularity, then it's another story. I'm
not saying WSJ is still printing solely because of OP but right now, it's 1.8 million print number
IS largely because of OP still existing. You cannot refute that and THAT was my point. Print numbers do matter to WSJ.
Also, you ask why are the numbers dropping if One Piece is the main reason people read WSJ? You've basically answered your question. If they read solely one piece, then they no longer have a need to read the magazine and therefore stop.
BUT the drop won't be a one time big thing. It happens gradually just like how volume sales drop for a series past it's peak. It doesn't drop in one go. People have their own speed at which they might stop buying the magazine. Some might give the magazine few more months to see if better series come along if they like ongoing ones and if not, they stop and just buy volumes. Some might still keep reading, some might give it few more years. That's why it's important for WSJ to get another big million seller. MHA can do it, but it's not a sure thing even tho it's numbers right now are still great. Maybe TPN can do it but it wouldn't last long enough to be considered a mainstay pillar.
I fully understand OP's place in the industry. I never denied that OP's readership wasn't the largest, just that its not the only thing holding up Jump. There are plenty of people that don't read OP weekly which is shown in the volume first printing. A example of this would be of Jump's first ever reprint for the finale of Kochikame.
https://www.animenewsnetwork.com/ne...irst-ever-reprint-thanks-to-kochikame/.108529
Even DB didn't move Shueisha to reprint an issue.
The reason is simple. Kochikame was way past its prime. It sold 30-40k a volume before it ended. So when it ended, due to the legacy it left behind and possibly all the old fans wanting to be a part of that history, many would've bought the magazine.
A very simple comparison is when a well known music artist passes away, you immediately see albums rush back into charts because people who would've absorbed their music another way (streaming or just singles) would want to also obtain the entire album.
Even more specific example, when LP's Chester passed away in July last year, 3 albums that were not certified platinum in US went platinum within 2 -4 months. One of those albums only even sold about 300k before then.
DBZ was at it's peak when it ended. WSJ was already at it's peak circulation because of DBZ. 6 million, if I'm not mistaken.
