As you may know, our world is dominated by economic concepts which evolved to fit the existing political models all the way from hunter-gatherer societies all the way to our modern financial system. But I don't want to talk about the real world with its real capitalism and its real communism or all that stuff, I'm here to talk about how things seem to work and why they work or why they shouldn't be working in our favourite series' universe. I will speculate on a lot of stuff, simply because Oda, although amazing at world-building, doesn't delve into too much detail about the processes.
To start off, we should discuss a little bit about the structures of society existent in One Piece. The World Government currently acts as the dominant political force and governs in an authoritarian fashion (to some extent), it is sovereign over all other nations that are affiliated with it (as it asks for a tax, offers security and establishes the legislation), it resembles a bit a federal government, but also a political union like the European Union. Regardless of the details, it has the typical branches we see in modern political systems of Executive power (The Gorosei), Legislative power (the Reverie, where all constituents of this giant "alliance" discuss issues and ways to handle them) and the Juridical power (Marine HQ-Enies Lobby-Impel Down), it has a common currency, a common spoken and written language and it kinda encompasses almost the entire inhabited world, the only powers strong enough to defy it being the Yonko's in the New World. The WG asks for a tax and offers its services (security).
The Problems of Government
Corruption and absolutistic power is rampant though and we all know it. Let me put into words why. The juridical branch acts as an extension of the executive power. The marines that should follow the law (which is established at the Reverie through agreements and such - example being the abolition of slavery as a sign of friendship when Fishman Island joined) are at the same time, the personal army of the World Government's HQ, Mariejois. Admirals that are summoned with the push of a button to follow the wishes of World Nobles that have no clue what the real world is like are a good enough show of corruption and absolutistic or authoritarian rule. But if you wish another proof, then Ohara's Buster Call moment and the information manipulation that took place in its aftermath should be enough.
It's no wonder that piracy is so common that people don't really care about pirates as long as they behave (such as Water Seven), the whole problem with the world is that the government is not doing its job too well. It isn't keeping the people happy enough or weak enough not to rebel. Of course, the thing that the government does is create further divisions (just as Doflamingo did with the people of Dressrossa and King Riku as he put a huge bounty on him) by rewarding those that take care of rebellions (Dragon having the highest bounty for a reason). Imagine being betrayed by your closest allies, because the world made your head worth a fuckton of money. In general, these divisions work. They worked with Law's country and most likely with many others that don't follow the rules.
You might wonder why not everyone in the world is rebelling, but it's simply because they are too limited in power, ambition, knowledge or are sufficiently happy with their lives. For the peasant, it doesn't matter which distant king governs him, it matters who doesn't send him to war, or ask for too much food in exchange for protection.
Now... protection is a big issue and this is why the New World is outside the WG's control in many instances. Pirates much stronger, which offer much better protection than the real government, can offer their protection. Even if in name, the police force exists to protect the citizens, in the real world, mafia's offer the real security to lenders (or very many cases, are using extortion methods, the methods are very diverse). No matter how much the WG paints the picture of pirates, those pirates might be more helpful than the biggest shark - which asks for money and gives nothing in return. Fishman Island is part of the WG, and yet it was WB's, Big Mom's - and is currently Luffy's territory and as such receives his protection (with him, paying no tribute or tax, or whatever you wanna call it). This is why, such an "informal" economy actually exists. Oda combines old and new systems of governance and this adds nuance to the story's protagonists, which travel in a dysfunctional modern political system which permits corruption based on authority, and where leadership based on value is the best way ahead (why people naturally follow Luffy's simple nature). Pirates, at least the honourable ones, offer a much more functional system, than the WG and the only reason they're bad is because the WG says so, it's directly manipulated our image of them, just as they did with Ohara.
Now, let's look at something very common in the real world, which in our modern world, has permeated our cultures, identities and lifestyles (along with technology of course). Trade is important, because you can't produce everything you use. It might be trade within a nation (you make food which I eat and I write the books you tell to your children who are dressed in the clothes someone else made) or between nations (our nations has coal deposits which you use for heat and yours has iron which we need for weapons). It's because of that, that so many places have very specifically-looking architecture, it's because the materials have to be procured locally, because of transport fees and problems with pirates.
Water Seven is a good place to discuss trade, because it created a high-speed, very effective network between 3 locations (hard to rob, can transport a lot) and could add tariffs to the trade and earn from it. It's also earning money from Tourism and its shipwright business, so it's no wonder that it is such a prosperous nation-city.
The city would have been lost without that trade as it had no natural resources to sustain it (food mainly). Nations that can sustain themselves and can have enough protection are generally the places where we don't see any rebellions or crises. Zou has both, hence its isolationary nature. Sky Islands and Fishman Island (before the technology was available) were isolationist too.
Compared to the modern real world, the world of One Piece does not really show signs of debt, so that single currency is incredibly valuable. You can get what you need or want (be it food or luxury) only with CASH (and in our world, cash is a very small percent of the total money in the world, about 8.3%, we mostly work with short debt, long debt and finally, whether you like it or not, complex bets XD), GOLD or other valuables that have an existing exchange rate to currency (basically, said cash), direct services or products (basic trade) and services (even the service of not hitting you in the face if you give me what I want/need).
It's because of this shortcoming that Alabasta went bankrupt. So lemme explain what bankruptcy is. Let's say you're Alabasta, and you can't produce any food anymore. You can offer your services for food, but everyone is too far away so you can't directly trade services, that would mean emigration (since people who want food, would go work for food where there is food, not Alabasta). You can trade your products for food, but hey, maybe nobody has enough food nearby to trade with you, before it goes bad (since food is a perishable product) so some peeps will still have to starve. You can sell the cash you collect through tax for food, or sell your gold for food, but the same problem remains. These are the barriers of trade. If Alabasta was a company, it could basically not sell its product for enough money to keep itself afloat. Now let's not forget that taxes could in this sense be a promise of availability of food, something similar to a debt. Alabasta can't pay its debts to its citizens aaaaaand... they're fucked. You go bankrupt when that time of the month comes when you have to pay your debt, but have no cash on hand, so you have to give something of enough value and if it surpasses what you owe, you have to pay with prison or death (in underground systems of course). Since nothing is more important than food, LET'S TAKE CONTROL OF THE KINGDOM AND KILL THE MONARCHY!
For any people well-versed in economics, I know the analogy is not a good way to explain it, but it's important to see how concepts such as liquidity translate can be extrapolated in many ways, because they're all semantic contraptions we have to understand the world.
To end, I would like to mention, the perks of an authoritarian global rule is THE BELLY (except for the very still isolated places like Skypiea which has an exchange rate to belly's). Woohooo, trade is so much simpler when the whole world knows that one belly is one belly! You know that everyone is talking the same financial language~ A UNIFIED CURRENCY
But it has a big problem :D
Its value is fully dependent on local conditions.
The issue with a global currency is that not all areas in the world are the same. Some are poorer, some are richer.... if you have a universal tax in Belly, you will lead the poorer places into starvation (talking about the WG's tax). The Belly as a currency suffers from what I would call "localized inflation".
To explain inflation, imagine that you have $10 and an apple is $1. Inflation happens when the apple is $2 and you still have $10. You will have to spend 20% instead of only 10% of your available money. Prices for products depend on how rich or how poor a region is in the resources necessary to produce said products or how cheap it is to import them from nearby.
The thing is... If you have something that can be exchange for a lot of Belly, like gold and silver, you can get a lot of money, but if you're rich in food, you get a lot lot less. If you are for example a civilization that has an abundancy of food and a strong military power to protect yourself, you may only trade for stuff that is not necessarily expensive, but also not necessary for sustaining your life, leisure items. You get taxed by the WG on your money, not your food, so a country with richer trade goods and decent food is going to be richer than a country rich in food, but with little other trade. If there is not enough demand for food, or you have a lower harvest, you won't get enough money produced to pay the taxes to the WG.
The thing that would logically follow is that the WG could buy the food from you for a discounted price. Something that might dry your riches so much, to the point that... you just say fuck it and become an insurgent.
If this was based on a food tax, instead of a tax on currency, your country would not have had an issue, but this thing happens in dictatorships where the power is desired to be centralized (weak, uneducated, disconnected people are easy to govern).
Logically, in One Piece diplomacy, as the WG, I would rather have your loyalty than your money, because... I own that money?
When a country in that example is forced to choose between the risk of being destroyed by a Marine force or starvation because the WG is stupid, it's clear that it will be much more desirable to rebel.
(As I remember, there was a tax collection ship that Doffy used for blackmail into his Shichibukai position and also mentions of how that tax led to poverty and starvation in countries)
Basically, any weak enough country would have to follow or be obliterated. Same technique Arlong used. But those that are strong enough would clearly rebel. Assistance from external powers that go against the WG is obviously beneficial (like Dragon or Yonko's)
Now... who prints the money? The WG. Who gives it its value? Everyone else. The WG cannot say in any way how much your water or your food must cost. Simply because it cannot enforce those prices, it doesn't have the necessary infrastructure. Only local governments can, and that's their problem entirely. Because of this, if local taxes are a bad deal for the people of an island, they can just as well enter the black market. And because of this lack of control and disparity of justice systems (as the marines are the main enforcers), the black market is so proliferated.
When you try to enforce a modern system, where it's so much easier to do it another way (as it happens in India and Pakistan where the infrastructure is bad and sometimes people don't have enough change or can't offer a bill), so... those exchanges won't get taxed and so it begins. Piracy.
The WG can print as much money as it wants. But let's say you have 100 people with $500 in circulation (how much they own combined) and you have 500 apples, each worth $1. If people in this metaphor need 5 apples to survive until they get a new batch (new harvest), everyone is fine. If there's $5000 in circulation, but you take away the number of apples... you'll have people competing have enough food so they won't starve, the prices of apples will rise (because the guys that sell apples aren't stupid and if they see people fighting over their product, they'll raise the price) and BAM, you get inflation. Lesson is, doesn't matter how much money exists, it matters how many resources exist and how the money is distributed.
Since Mariejois has control over a very important resource, military might, it has the privilege to collect taxes and control wealth. This imbalance of power and inefficient authoritarian control is the exact reason why we're in the GREAT PIRATE AGE. Wealth means power, and a lot of people don't like the way things are, because the WG isn't doing too good of a job at operating this complex world by using a single currency.
For that same reason the Celestial Dragons have billions of belly's in their "banks". In Mariejois, they certainly don't even use currency, because all their needs are fulfilled by executive power. Their orders are commands that cannot be disobeyed. And because Mariejois prints all the money, they can just toss out billions of belly without any issues. They will only need to raise the taxes afterwards to get the money back (which is in a sense stealing, because that money that they toss around might never reach the people at the furthest islands, only their obligations do). For that reason, I am sure (regardless of what Oda might have said), a cabbage might be worth a lot more on Sabaody, because there's more cash flowing in and even more in the New World, where it might be a damn freaking precious resource. Money will certainly not have the same value in different places. And I can guarantee, this is also the reason why bounties are so huge in the New World. There's a lot more money to go around and even if the people are not just as powerful of a threat, only high enough bounties could motivate NW mercenaries to move their bums for a hunt. Since there is more wealth, there will also be stronger people will make bounties even higher. But I would consider non-isolated, new world nations to have more money than others around the world, simply because trade could not take place, if you don't pay enough for security.
What I am absolutely fascinated about is how a single gold trader in Water Seven had enough freaking cash on hand to buy all of the SH's gold. Especially considering how in a time of crisis, 10 bn was barely possible for a king to gather in taxes (the available cash of the citizens and the royal family) in a decent-sized kingdom. That's only 33 times more than what one single trader could muster in a day. I can, but only imagine that the guy had to call every single trader in Water 7 to get all that currency in one place XDXD. It is quite a feat. So much else he could have done with that money... Either way. I wanna talk about a very interesting system which is in use in our current arc.
The Soul Economy
Big Mom uses a very interesting tax on her citizens in exchange for protection and it is making me very curious about the general flow of Belly in her economy, but still, I am bedazzled by it either way.
In exchange for pieces of their soul (and some totalitarianism), Big Mom provides the protection very few can offer (definitely not the Marines in the New World). That soul equates to lifespan aka Time. Metaphorically, it is exactly what our modern tax system does. In exchange for social services, infrastructure, education, health and protection, we give away a part of our hard-earned cash. We earn that money by using our precious time (and skills duh). So, kinda, somewhat, in a way... There isn't that much of a difference. In the end, the people still need their skills to have a functioning society (they still need to earn their food and possibly other stuff like health, infrastructure, etc) and there, real money may be used. It would be interesting to think that she might also use her homies to boost the economy (building houses, roads, helping in trade and administration) since that would be just the same as paying wages to workers (in this case, absolutely loyal public servants). That is something I might predict happening, as the toys were used in Doflamingo's case.
I would love to discuss her economic model and go further into speculation about it, but sadly enough, I need to finish this blog, because I'm tired of writing.
I hope I could provide a coherent enough discussion about the more practical aspects of One Piece's systems, and I apologize if my style was a little awkward or hard to decipher. I haven't written a blog in a while. Thank you :D