Relearning Economics Profile picture
Aug 15 10 tweets 2 min read Read on X
Mainstream econ says:
Households save → banks lend savings → firms invest.

Robinson flipped it: investment comes first, savings follow.

Once you see how money & banking work, it’s hard to unsee.
🧵1/10 Image
The Goodwin growth cycle shows it:
Investment drives output & jobs → higher employment boosts wages → rising wages can squeeze profits → investment slows → cycle repeats.

It starts with investment decisions, not household savings.
🧵2/10
So where does the money for investment come from?

Not from a “pool” of prior savings.

Modern banks create credit.

When they lend, they create deposits, new money instantly funding investment.
🧵3/10
Firms borrow → spend → raise output & incomes.

Only after incomes rise does saving appear in the data.

In national accounts, investment = saving — but causality runs from investment to saving, not the other way.
🧵4/10
If households save more by spending less, firms sell less.

Lower sales → lower profits → less investment.
Without another source of demand (govt deficits, exports), higher saving today can actually reduce investment.
🧵5/10
Keen’s extensions to Goodwin add private debt:

Firms invest if profitable demand is there.

If profits aren’t enough, they borrow, banks create the credit they need.

Again: credit & investment lead; savings follow.
🧵6/10
Policy flip:
If you want more investment, don’t push for more saving first.

Give firms reasons to invest & ensure credit supply.

The saving will happen automatically as a byproduct of higher incomes.
🧵7/10
If households cut spending & no one else fills the gap, the cycle reverses:

Investment slows → incomes stagnate → savings vanish.

High saving without offsetting demand is self-defeating.
🧵8/10
In a credit-creating economy, investment is the engine.

Savings are just the shadow it casts.

Robinson’s line isn’t just rhetoric, it’s a basic truth about how monetary economies work.
🧵9/10
We should stop designing policy as if savings are the fuel for growth.

Investment decisions, backed by a banking system that can create credit, come first.
📖 Full blog here →
🧵10/10
patreon.com/posts/investme…

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More from @RelearningEcon

Aug 11
Mainstream macro blames crises on public debt or bad policy.

History tells a different story, The biggest crashes follow private debt booms , when households & firms load up on credit faster than incomes grow.
🧵1/8 Image
1929, Japan’s 1990s bust, the 2008 GFC, all preceded by surging private debt-to-GDP.

In each case, public debt rose after the crisis, as governments absorbed the fallout.

Cause and effect are backwards in the textbook story.
🧵2/8
Private debt booms are dangerous because they fuel asset bubbles and fragile balance sheets.

When cashflows falter or rates rise, defaults spike and leverage turns into a chain reaction.
🧵3/8
Read 8 tweets
Aug 7
Fractional reserve banking" still shows up in textbooks, news, and even heterodox debates.

But the concept is dead.

Modern banking doesn’t work that way, and clinging to the term misleads more than it explains.
🧵1/9 Image
Traditionally, it meant banks held a fixed % of deposits in reserve (say 10%) and lent out the rest.

But today?

There are no reserve requirements in countries like the U.S.

Banks aren’t lending most of your money. They aren’t required to hold any.
🧵2/9
Bank lending today is constrained by:
– Capital ratios
– Liquidity rules
– Risk appetite

Banks lend when it’s profitable, not when they have “extra reserves.”

In fact, they don’t lend reserves to the public at all — only to other banks.
🧵3/9
Read 9 tweets
Jul 30
Neoclassical models treat fiscal policy as neutral in the long run, only useful in “crises.”

But this idea rests on flawed assumptions: full employment, crowding out, Ricardian equivalence, and perfect markets.

Let’s unpack why none of these hold.
🧵1/7 Image
Assumption: the economy naturally returns to full employment.

Reality: underemployment, labor market hysteresis, and demand shortfalls are persistent.

When you assume away slack, you assume away the need for fiscal intervention.
🧵2/7
Assumption: government spending crowds out private investment via interest rates.

But when the central bank controls the rate, and firms face uncertain demand, this logic fails.

Spending creates income, not competition for funds.
Read 7 tweets
Jul 28
Mainstream macro relies on rational expectations: agents are assumed to know the model and forecast the future accordingly.

But real economies aren't solved backwards.
The Deep Minsky model throws this out, and models how expectations actually evolve.
🧵1/7 Image
Instead of perfect foresight, Deep Minsky agents adapt using feedback:
-Flows inform future behavior
-Perceived trends shift confidence
-Expectations are path-dependent

This lets the model evolve historically, not jump from equilibrium to equilibrium.
🧵2/7
In Deep Minsky, investment, consumption, and pricing decisions respond to changing financial conditions, not "optimal" plans.

Expectations are formed endogenously, through firm behavior, bank leverage, and wage–price dynamics.
🧵3/7 Image
Read 7 tweets
Jul 27
In the 1960s, MIT's Jay Forrester created a simulation that changed how we think about supply chains: the Beer Game.

It revealed that even stable demand can cause wild production swings—now known as the bullwhip effect.
🧵1/10 Image
The game has 4 roles: Retailer, Wholesaler, Distributor & Factory.

Each tries to meet demand & manage inventory—but only sees demand after it’s placed. That delay leads each player to guess, and missteps quickly multiply.
🧵2/10
If the retailer slightly overorders, the wholesaler overreacts, the distributor does the same, and the factory ramps up too much. That overcorrection leads to big swings—causing stockouts or bloated inventories.
🧵3/10 Image
Read 10 tweets
Jul 25
Mainstream macro uses the NAIRU, or the Non-Accelerating Inflation Rate of Unemployment, as a constraint.

If unemployment falls “too low,” inflation is expected to rise uncontrollably.

But this framework misrepresents both data and Phillips’ original insight.
🧵1/7 Image
In 1958, Phillips published a paper showing a statistical relationship between wage inflation and unemployment in the UK, not a structural law.

He didn’t claim there was a “natural” rate or a threshold.

It was a historical pattern, not a causal rule.
📎 Phillips (1958)
🧵2/7
Phillips warned this relationship could shift with institutions, union density, labor laws, bargaining regimes.

Modern NAIRU theory ignored that.

Instead, it imposed a fixed trade-off and turned an empirical curve into a universal policy constraint.
🧵3/7
Read 7 tweets

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