When Members Aren't Identical

Up to now, every member in these simulations has been a clone. Same monthly spend, same target, same finish line. That is a convenient fiction, and a fragile one. A cooperative economy that only balances when everyone needs exactly the same amount to live is not a model of people. It is a model of a spreadsheet.

Real families are not clones. One household lives on a modest budget. Another is larger, or lives in a costlier place, and needs several times as much to reach the same security. If the model is going to mean anything, it has to graduate them — the actual, unequal them. And it has to do it fairly. So we took the clones apart.

We added a single dial: spend spread. At zero, everyone is identical again, and the model reproduces its earlier results exactly — nothing else changed. Turn it up, and each member is handed their own monthly spend, drawn from a realistic distribution. Most families sit near the middle. A long tail has larger budgets, the biggest several times the smallest.

Each family's own spend becomes their own graduation target. "Full coverage" no longer means one shared number. It means your income has grown to meet your cost of living. A member is done when their permanent income covers their own budget — not the average, not their neighbour's. The community is done when the last family gets there.

This is a harder test than it sounds. A big-budget family needs far more income to be covered. And the model's rules deliberately hold everyone in lockstep: no one climbs more than one coverage level per cycle. It would be easy for the high-need families to be left permanently behind. Or the whole community could stall short of the line. Does it?

Below, the model runs across the spend-spread dial (default settings, seed 12345). Identical budgets sit on the left. A wide, realistic spread sits on the right. For each run, we plot three things: how unequal the resulting incomes are, how unequal the resulting coverage is, and when everyone graduates.

Three findings, and none of them was guaranteed:

• Everyone still graduates. At every spread level, across every seed we tried, not a single family is left behind. Each one reaches its own full coverage.
• The clock doesn't move. Whether budgets are identical or spread wide, the community graduates in essentially the same time. That is a touch under eleven years. If anything, it is slightly faster as the spread grows.
• Coverage stays equal; income does not. The teal line is inequality of coverage — how close each family is to being secure. It stays pinned near zero. But the gold bars, inequality of raw income, climb steadily. The bigger families end up earning more.

That last pair is the whole point, and it deserves its own section.

When absolute incomes fan apart, the reflex is to worry that inequality is creeping back in. But look at who earns more. In this model, the correlation between a family's spend and its final income is almost perfect: around 0.99. The families that end up with the largest incomes are, almost exactly, the families with the largest budgets.

That is not inequality leaking in. It is the system doing exactly what it should: income rises to meet need. A household that needs three times as much to live ends up earning about three times as much. And it lands at the same place everyone else does: fully covered. The spread in incomes isn't a gap between winners and losers. It is the shape of different lives being carried to the same security.

So the right way to read the two lines is this. Coverage is whether your family is safe — the thing that actually matters. It is held equal for everyone. Income is the raw number. It is allowed to differ exactly as much as needs differ, and not one bit more. The model separates the number that should be equal from the number that shouldn't be. It keeps each where it belongs.

There is a deeper idea underneath this, one worth naming. Call it invariance of opportunity. In most economies, your starting conditions bend your whole path. How much you need, and where you begin, decide whether you ever arrive at all. Here they don't. Your budget sets where your finish line is. The model moves the line to meet you. Then it carries you to it on the same schedule as everyone else.

Two families who contribute alike travel the same journey to security. That holds even if one needs a modest income to get there and the other a large one. The destination is personal; the journey is shared. That is a strong claim. For this first slice of heterogeneity, at least, the model actually delivers it.

The first thing you do to a model that works on identical people is make the people different. That is the first thing reality does. A design that balances only under the fiction of sameness hasn't been tested. It has been flattered.

This one survives the test. Hand every family its own budget, as unequal as you like. The machine still carries all of them to their own security, in the same time. Income rises to meet need rather than pulling apart from it. It is not a spreadsheet that happens to balance. It is starting to look like a model of people.