The Tax Research glossary seeks to explain the terms used on this blog that refer to more technical aspects of economics, accounting and tax. It recognises that understanding these terms is critical to understanding the economic issues that affect us all the time.
Like the rest of the Tax Research blog, this glossary is written by Richard Murphy unless there is a note to the contrary. It is normative approach and reflects post-Keynesian, heterodox economic opinion with a bias towards modern monetary theory. The fact that many items in that sentence are hyperlinked shows that they are explained in the glossary.
The copyright notices pertaining to the Tax Research blog apply to this glossary.
The glossary is designed to achieve three goals:
- It seeks to provide a short, hopefully straightforward, definition of what a term might mean.
- It then seeks, when appropriate, to explain what the term means within the context in which it is used. This is meant to elaborate the definition to add to understanding.
- It then critiques the term, explaining, if appropriate, what the weaknesses inherent in the term or the situation it describes are. The aim here is to empower the reader to understand the issues behind the nonsense that most professions create around their activity to provide them with a mystique that they rarely deserve and which often hides what they are really up to.
The glossary is not complete. It will grow over time. If you think there are entries that need adding please let me know by emailing glossary@taxresearch.org.uk. Please also feel free to suggest edits. The best way to do this is to copy an entry into Word and then send me a track-changed document indicating the changes that you suggest.
Because of the way in which it is coded this glossary automatically cross refers entries within itself and to the blog that it supports and within the glossary itself but if you think a link is missing please let me know.
Finally, if you like this glossary then you might like to buy me a coffee. It has required the support of a fair few to write it. You can do so here.
Glossary Entries
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
- Economically active population
- Effective interest rate
- Enterprise zone
- Equilibrium
- EU Code of Conduct on Business Taxation
- Exchange traded funds
- Excise duties
- Export Processing Zones
- Externality
- Extreme centrism
Economically active population
The economically active population of a place comprises "all persons of either sex above a specified age who furnish the supply of labour for the production of economic goods and services (employed and unemployed, including those seeking work for the first time) during a specified time reference period." (OECD).
The proportion of the population that is economically active can be a useful indicator of the health of an economy and its capacity for growth. The ratio can, however, change between jurisdictions because of differing social norms.
Effective interest rate
Enterprise zone
Equilibrium
Equilibrium
At the heart of neoclassical economics lies a comforting faith: that markets are naturally self-correcting. Left alone, they supposedly return to equilibrium after any disturbance. It is an appealing story and one that excuses inaction. But history keeps disproving it.
Assumption
The assumption is that markets, like physical systems, tend toward balance. If demand exceeds supply, prices rise, encouraging more production and less consumption until the gap closes. If supply exceeds demand, prices fall. Shocks are temporary, and the system restores itself. This belief underpins the idea that governments should not intervene except to remove obstacles to adjustment.
Reality
Real economies are never in equilibrium. They are dynamic, evolutionary systems full of feedback loops, herd behaviour and uncertainty. Financial markets amplify shocks rather than dampen them. Booms create bubbles; bubbles breed collapse. The 2008 crisis, like those before and after it, was not an anomaly but a manifestation of inherent instability. Small imbalances can snowball into systemic breakdowns because expectations, debt and confidence interact in unpredictable ways. Path dependence means history matters: once a market collapses, recovery can take years or decades.
Moreover, economies are embedded in society and nature — both of which have thresholds and tipping points. Climate change, for example, shows that “equilibrium” can be permanently lost.
Why It Matters
The myth of self-correction justifies political passivity. It tells governments that markets heal themselves, that unemployment will adjust, and that crises are momentary. In truth, only active fiscal policy, regulation and public investment can restore stability. Economies are living systems that require care, not clockwork that requires no attention. The pursuit of equilibrium has made economists blind to instability, the very feature that defines capitalism.
Summary
Markets do not self-correct; they self-destruct unless society chooses to manage them. Equilibrium is part of the mystical and mythical belief system of neoclassical economics, but bears no relationship to any known state that exists in any economy.
EU Code of Conduct on Business Taxation
The EU Code of Conduct on Business Taxation promotes fair tax competition both within the EU and beyond.
The original Code of Conduct was agreed by EU finance ministers in 1997 as an intergovernmental, legally non-binding instrument. It has been primarily used to identify and assess preferential tax measures (i.e. measures that provide for a lower level of taxation than the level which is applicable in general) that are possibly harmful.
On 2022 the Ecofin Council approved a revised Code of Conduct, broadening the scope to include not just preferential tax measures but also 'tax features of general application', which create opportunities for double non-taxation or can lead to the double or multiple use of tax benefits.
Exchange traded funds
Exchange traded funds (ETFs) are collective or pooled investment funds that are quoted on stock exchanges.
The funds usually have a very narrow focus. They do, for example, invest in government bonds, or a particular stock exchange or commodity index. They might also have a particular sector focus.
Exchange traded funds provide a compromise between collectivising risk and targetted investing.
The big concern with ETFs is with regard to their liquidity in the event of rapid changes in the perception of the value of either the fund or the underlying sector in which they invest.
Excise duties
Excise duties are specific sales taxes usually added to the price of goods that are considered harmful or which create a specific economic externality.
Excise duties are commonly applied to tobacco, alcohol and carbon-based products but can be used for other purposes.
Excise duties are very effective revenue-raising taxes, partly because of the price inelasticity of demand for many of the products to which they are applied, e.g. cigarettes, which are consumed by those addicted to nicotine whatever the price charged.
The revenue raised is often dependent upon the ability of a jurisdiction to control smuggling and illicit products. Excise duties have a social as well as a revenue function (see entries on the reasons to tax).
Export Processing Zones
Export processing zones are artificial enclaves within states where the usual rules relating to taxation and regulation are suspended to create what are, in effect, tax havens within larger countries.
The rules that are relaxed may be for import and export taxes or corporation taxes or all three and may also extend to relaxing other regulations e.g. on health and safety or the environment. There may also be a relaxation of local taxes e.g. land taxes and social security charges.
See also freeports, of which these zones are a type.
As with all freeports, these zones are open to abuse, fraud and criminality, because of the relaxed regulation that tends to typify their operation. There is little evidence that they add economic value to the locations that host them.
Externality
Externalities are the costs that a product gives rise to which are not usually reflected in its sale price because they are borne by society at large and not by the specific consumer of the item made available for sake e.g., the pollution from driving a car is an externality the cost of which the motorist does not directly bear.
Excise duties are often used to correct for the cost of externalities.
Tax externalities can arise from the impact one tax or the practice associated with one tax base can have on other taxes or tax bases, both within and between countries. These externalities are also known as tax spillovers.
Extreme centrism
What is Extreme Centrism?
Extreme centrism is not moderation. It is not the balanced, thoughtful negotiation between political extremes. Instead, it can be described as a radical form of political inaction, disguised as neutrality, which prioritises preserving the status quo above all else.
It is, at heart, deeply conservative, but unlike traditional conservatism, it avoids scrutiny by wearing the respectable mask of reasonableness. It positions itself in the “centre” of politics—claiming to rise above ideology—while in reality, it defends existing power structures, economic inequalities, and institutional failures by refusing to question or change them.
Key Features of Extreme Centrism
-
Status Quo Above All Else
Extreme centrists argue that their role is to keep things “stable” and “sensible.” But what they actually protect is the existing system—flawed and unjust as it may be. They claim to be pragmatic, yet they treat current arrangements as immutable, regardless of the harm they may cause.
-
Managerialism, Not Vision
These politicians frame their work as technocratic competence: balancing budgets, tweaking regulations, and fine-tuning systems. But this is not leadership—it's administration in the face of crisis. The world may be heading for the rocks, yet they believe their job is to “steady the ship,” rather than change its direction.
-
Resistance to Reform
Whether it's on inequality, climate action, or democratic accountability, extreme centrists resist the big ideas that social and ecological crises demand. To propose real alternatives is, in their view, irresponsible. But in clinging to “business as usual,” they deny the reality of the moment we are living through.
-
Moderate in Name Only
Their language is couched in the language of caution, restraint, and “balance.” But this is misleading. By actively blocking transformation, extreme centrists often become more dangerous than overt conservatives, because their apparent neutrality allows them to undermine progress with far less public scrutiny.
Why Is This a Threat?
Extreme centrism is a political dead end. It pretends that we live in a world where only minor adjustments are needed—when in reality, we are living through polycrises: climate collapse, economic inequality, democratic decay. The centrists' refusal to acknowledge or respond to this with urgency is a threat in itself.
By claiming to offer safety, they dull public awareness of the real dangers ahead. By marginalising radical ideas as “unrealistic,” they block the emergence of alternatives. And by doing so, they leave the political space open to reactionaries and authoritarians who promise decisive action—however misguided or dangerous it may be.
In Summary
Extreme centrism is:
-
Conservatism in disguise, cloaked in the language of balance.
-
A refusal to act, masquerading as political responsibility.
-
A barrier to progress, posing as maturity and good governance.
-
A threat to democracy, because it suppresses the debate, vision, and ambition required to build a better future.
It is not the safe middle path—but a form of extremism in its own right.

Buy me a coffee!
