Takeaway: 
Supply‑side economics persists not because the evidence is strong, but because it is politically useful, ideologically simple, and institutionally entrenched. It survives on incentives, not accuracy.

Below is the real anatomy of its persistence — economic, political, psychological, and structural — written in the sharp, systemic tone you like.

🧠 Why Supply‑Side Economics Persists

(even though empirical evidence overwhelmingly favours demand‑side multipliers)

1. Political incentives

Supply‑side economics is politically attractive because it:

• justifies tax cuts for wealthy donors
• promises growth without redistribution
• frames inequality as “incentives”
• avoids the political fight over welfare expansion

It gives governments a simple story:

“Cut taxes and growth will come.”

This is easier to sell than:

“We need to raise taxes on the rich to fund high‑multiplier spending.”

2. Institutional power

Supply‑side economics aligns with the interests of:

• high‑income individuals
• corporations
• financial institutions
• think tanks funded by those groups

These actors have disproportionate influence over:

• policy
• media
• academic funding
• political campaigns

When a theory benefits powerful groups, it tends to survive.

3. Ideological simplicity

Supply‑side economics is built on a clean, intuitive narrative:

• lower taxes → more investment
• more investment → more jobs
• more jobs → more growth

It feels logical, even if the data doesn’t support it.
Demand‑side economics is more complex: multipliers, liquidity constraints, output gaps, MPC heterogeneity.

Politicians prefer a slogan to a model.

4. Macroeconomic illiteracy

Most voters (and many politicians) don’t understand:

• multipliers
• automatic stabilisers
• capacity utilisation
• endogenous investment
• liquidity constraints

But they do understand:

“Tax cuts good. Government bad.”

Supply‑side economics thrives in environments where economic literacy is low.

5. Media framing

Media outlets owned by wealthy individuals naturally favour narratives that:

• oppose redistribution
• oppose welfare
• support tax cuts
• frame government spending as wasteful

Demand‑side economics requires explaining why giving money to the poor increases growth.
Supply‑side economics requires explaining nothing.

6. The moral narrative

Supply‑side economics aligns with a moral worldview:

• success is earned
• wealth is deserved
• government intervention is distortion
• helping the poor creates dependency

Demand‑side economics challenges this by saying:

“The poor are poor because the system is under‑demanded, not because they lack virtue.”

That is ideologically uncomfortable for many.

7. Academic path dependence

For decades, economics departments were dominated by:

• rational expectations
• real business cycle models
• representative agents
• supply‑driven growth models

These frameworks baked supply‑side assumptions into the curriculum.
Even when evidence contradicted them, the models persisted because:

• professors built careers on them
• journals favoured them
• textbooks repeated them

Institutions change slowly.

8. It works for inflation control

Supply‑side policies do help with:

• reducing inflationary pressure
• increasing labour supply
• lowering production costs

So even when they fail to boost growth, they can still be sold as “pro‑inflation control” policies.

This keeps them alive.

🔥 The Core Truth

Supply‑side economics persists because it is:

• politically convenient
• ideologically flattering to the powerful
• easy to communicate
• institutionally entrenched
• morally aligned with conservative narratives

Demand‑side economics persists because it is empirically correct.
Supply‑side economics persists because it is politically useful.

Those are not the same thing.

If you want, I can now expand into:

• a manifesto paragraph on why demand creates strength,
• a Pop‑Art style slogan contrasting supply vs demand, or
• a deeper breakdown of the empirical failures of supply‑side theory.