assembly-economics/models/GADM-0.4.md

Generative Assembly Dynamics Model — GADM-0.4

Status: in development, exploratory. Implemented so far: durable human capability (§ 1, ASSEMBLY-WP-0006-T01), grounded organism depreciation and robustness checks (§ 2, T02).

GADM-0.4 builds on the GADM-0.3 cohort model (GADM-0.3.md § 5), which stays unchanged and reproducible in gadm03c.py. Time unit: one year.

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1. Durable human capability (T01)

1.1 Motivation

GADM-0.3 failed hypothesis L3: an education push reached working-age capability after only about 9 years, and weakly. Working-age capability had no memory of childhood, because it relaxed to current conditions within about 8 years.

1.2 Structure

Each cohort's capability is split into:

Component	Formed by	Depreciation (per year)	Carried by ageing
durable D_c	education in childhood (hform, scaled by edu, plus commons X); small lifelong formation for adults (ll)	0.01 (children, working age), 0.02 (seniors), 0.04 (very old)	yes
current C_c	GADM-0.3 cohort dynamics (learning, mentoring, deskilling, care)	as GADM-0.3	yes

Effective cohort capability: H_c = \tfrac12 D_c + \tfrac12 C_c. Aggregate H, which the rest of the model uses, is population-weighted as in GADM-0.3.

Two couplings:

• Learning begets learning: a cohort's current-capability gains are scaled by 1 + lbl\,(D_c - 0.5).
• Birth dilution: newborns enter the children's cohort with no durable capability, so the cohort average is diluted at the birth rate (about 1/20 per year). A first draft omitted this term; durable capability then saturated near 0.85, leaving no room for an education effect.

Initial values: D_c = C_c = GADM-0.3 H_c, so effective capability starts identical to GADM-0.3 (unit-tested).

1.3 Results

Computed at T01, before dO was grounded (§ 2). The grounded values differ by at most 0.004.

	GADM-0.3 cohorts	GADM-0.4
Baseline VFAC (t = 100)	0.323	0.323
Generative regime VFAC	0.656	0.661
L3: education +50 % → final ΔH working age	+0.010	+0.032
L3: years to half of that effect	9	17 (durable part: 21)
L1: ageing + strong mentoring (tg 0.15), ΔH	−0.018	−0.029
L1: stable, no mentoring, ΔH	−0.043	−0.039

Full tables: simulations/gadm02/results/life_cycle_gadm04.md.

1.4 Readings

1. L3 is now supported. Education reaches working-age capability with a 17-year half-time, inside the hypothesised 15–20 years, and with three times the effect. The lag comes from cohort turnover (about 2.2 % per year) plus slow durable depreciation. The relaxation time is about 1/(0.01 + 0.022) ≈ 30 years.
2. L1 still holds, more weakly. Mentoring acts on current capability only, so its leverage on effective capability halves. An ageing society with strong mentoring still loses less than a stable society without it.
3. Macro results are almost unchanged. Durable capability adds memory, not level: baseline and generative VFAC move by at most 0.005. Policies on education matter mostly beyond a 20-year horizon, which strengthens the case for longer simulation horizons in cohort experiments.

1.5 Limitations

• The split ½ / ½ between durable and current capability is assumed.
• Children's current capability (inherited from GADM-0.3) still has no birth dilution. Only the durable component was corrected.
• hform was chosen so that baseline children's durable capability settles near 0.6. It has no empirical anchor yet (see T02).

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2. Parameter grounding (T02)

Details and sources: ParameterGrounding.md.

• Organism depreciation is grounded: dO = 0.20 per year (evidence range 0.15–0.35, from software, R&D-capital and AI-hardware depreciation), instead of 0.06. Investment, learning and seeding are rescaled (×3.33) so the baseline organism path is unchanged. The evidence changes the timescale; the level of organism capability remains ungrounded.
• The key readings are robust to the grounded dO and to brackets on the ungrounded channel self-reinforcement (0.15–0.45) and wealth conversion (0.02–0.20). One exception: P3's effect size grows to −0.078 at strong self-reinforcement.
• With grounded dO: baseline VFAC 0.325, generative regime 0.665. The life-cycle results are essentially unchanged: L3 half-time 17 years, final ΔH working age +0.032; L1 ΔH −0.028 (ageing, strong mentoring) against −0.038 (stable, none).

Reproduce

python3 -B -m unittest discover -s simulations/gadm02
cd simulations/gadm02 && python3 -B life_cycle.py --model gadm04
cd simulations/gadm02 && python3 -B robustness.py      # T02 robustness checks