What phenomenon are at play such that the "Big Four" are limited to four and not a growing list?

Question

I've heard a list of anime referred to as "The Big Four":

1. Dragon Ball Z
2. Naruto/Naruto Shippuuden
3. One Piece
4. Bleach

What phenomenon are at play that there aren't more than 4 anime like these?

I think the criteria to get into The Big Four are along these lines:

• based on manga
• long running anime (hundreds of episodes)
• longer or concurrently running manga
• possibly currently running anime (they got their name when Bleach was still airing, so 3/4 were running for a while)

I've seen other shounen series pass 100 episodes, and there are certainly other fan favorites. There are also really long-running series geared towards children. However, it seems that most anime nowadays is 12 episodes, and maybe a followup season of another 12 episodes. I can't help but think that these phenomena are related.

Answer 1

I've heard a list of anime referred to as "The Big Four":

The first thing to be aware of is this: the idea of the "Big Four" is localized to the English-speaking / Western (possibly just North American?) fanbase. There is not an equivalent notion in Japan. This strongly suggests that an explanation for the "Big Four" must involve an understanding of the habits of English-speaking fans.

What phenomenon are at play that there aren't more than 4 anime like these?

I tentatively am inclined to attribute this idea to the fact that the current crop of teenagers and young adults who are the primary inhabitants of English-language anime discussion websites grew up watching these four shows (in, say, the late '90s and early '00s). All four of these shows had a number of properties that were instrumental to their having broad popularity among the demographic in question. In particular:

• they were dubbed in English
• they were extensively aired on readily-available television channels (especially Toonami)
• they were not "kid's shows" in the same way that something like Pokemon or Digimon is
• they had multiple hundreds of episodes

The only other show that comes to mind with these properties is Sailor Moon, and for simple demographic reasons, it's unlikely that fans of the "Big Four" would be fans of Sailor Moon, and vice versa.

So why is this list unchanging? Well, I expect that the list will change in a few years, when more older viewers phase out of online discussion sites and more younger viewers phase in. (This is a simple consequence of the demographics of anime discussion on the internet - older people get lives and stop watching/discussing anime, and new youngfolk with nothing better to do figure out how to internet and start posting about things in their stead.)

These younger viewers will likely have less exposure to Dragon Ball Z (and perhaps Bleach as well) and more exposure to the newest show that has all those properties: Fairy Tail. Perhaps there will be a "New Big Three" in 2020, consisting of Fairy Tail, Naruto, and One Piece.

However, it seems that most anime nowadays is 12 episodes, and maybe a followup season of another episodes.

This was already the case by the time One Piece started airing in 1999 (and even earlier than that), roughly speaking. Forever-running shows like the "Big Four" have long been in the minority. You, the English-speaking viewer, likely just didn't notice this during your younger days when you watched the "Big Four" on television, since these shorter, one-to-two cour shows were less likely to be dubbed and shown on television (and if they were, they probably wouldn't be shown during cartoon primetime).

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I should add that I am more aware of the idea of the "Big Three" (those four minus Dragon Ball Z) being a thing in the zeitgeist; and indeed, I suspect this is probably because Dragon Ball Z finished up a long time ago, and hence is not in vogue with the current crop of people who discuss anime online. (Whereas: Naruto and One Piece are still running, and Bleach ended only relatively recently.)

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Random832 also points out in a comment that one article from 2012 claims that the "Big Three" consists of Bleach, Naruto, and Inuyasha. This brings to mind an important point: there is no "official" notion of a "Big Three" in anime - I'm not aware of any industry sources that use the term. The "Big n" is what the internet makes of it; no more, no less.

Answer 2

As said by a user on Reddit:

The term was made to refer to those three manga because for a few years (~2004-2009/10) they were absolute juggernauts in sales and popularity rankings. The term "big three" stuck despite Bleach's popularity falling off (starting in ~2008) and Naruto losing a bit of ground over the last few years (largely in the Ninja War arc) as well.

You can find an article on The Big Three over here, because as Senshin puts it in his answer, the concept of The Big 3 is much more popular than that of The Big 4. To be honest, I hadn't even heard of that term before reading this question.

As per the article

Many fans agree that a title serialized in monthly installments could not due to a lower publication frequency, which encourages less fan discussion from week to week. It has been suggested that a Big 3 title could come from Weekly Shounen Magazine, which is Weekly Shounen Jump's closest rival. In this case, the most often cited candidate tends to be Fairy Tail. Some fans have pointed out that other Big 3's have existed in the past. In the early 90s, the Big 3 was said to have been Dragon Ball, Slam Dunk, and Yuu Yuu Hakusho. This era is thought of by many people as the Golden Age of Weekly Shounen Jump, when its circulation was at its peak. A few fans have said that One Piece, Rurouni Kenshin, and Hunter x Hunter were the Big 3 of the late 90s. Most people admit though that no other three titles have dominated for as long as the current Big 3.

If you check out the List of best-selling manga, it'll be pretty obvious why Dragon Ball, One Piece and Naruto form a part of The Big Four. As for Bleach, the manga had started off pretty strong and the sales were pretty high during the 2001-2010 period.

Currently, the Big 3 are One Piece, Naruto and Bleach and have been since 2004.

This proves that it's mainly the manga which dominates in deciding which series is a "Big One" because Bleach started airing in 2004 and was by no means a long anime. However, a long running anime and a well received one always gives the manga sales a boost and hence is indirectly a factor in deciding which series belongs to the list. However, it's definitely not the main factor. Atleast not for the current Big 3/4.

What phenomenon are at play that there aren't more than 4 anime like these?

I found a perfect reply to this question here:

For me, the big three always seemed to represent the rising popularity of manga. As each series got underway and gained momentum, so did the manga scene itself. These three shounen manga appeal to a specific audience - in my opinion - specially new readers. The manga are relics of a time long past; an era long forgotten. I don't think anything can replace any of these manga, just like how nobody really compares the big three to Dragon Ball Z. I don't actually think there is significance in these two manga ending, they've been long overdue as their quality has dropped significantly. The only thing to take away from this is how prevalent and awesome One Piece is. One Piece feels like it's still in its prime. I assume new readers will still start with Naruto or Bleach or One Piece, they still exist. No matter what new shounen appears, it'll hardly attract as much attention as these three. Otherwise, there would've been a shounen of similar caliber, considering how many years have passed. Some people thought Fairy Tail was a contending shounen, but readers know how that went. The only interesting part of all this is the fact that there exists an older generation who still follow manga and have more developed tastes, which has prompted a significant rise in seinen popularity over the years - in my opinion.

What I have to add on to this is: I feel it's unlikely for the list of Big Three or the Big Four to expand or be replaced in the near future. The only thing that's really stopping that is the existence of a long running manga which dominates in sales and appeals to a good age variety. Most of the top yearly manga sales is dominated by those manga (except of the Big Three) which have received an anime adaption in the near past (case in point: 2015 Manga Sales, 2014 Manga Sales, 2013 Manga Sales and so on). Most of those manga are short ones which are destined to end in the near future.