There is a real result in this data, and it is not the one usually told. Line up every critical material by how its production concentration changed and they split into two camps pulling in opposite directions. That split — not a tidy class trend — is the finding, and it needs no comparison group to see: the materials are compared only to their own past. The single tidiest claim you can make from a group average, “critical minerals are concentrating,” turns out to rest almost entirely on two of them.
The whole distribution, one dot per material
Each material’s change in production HHI, 1995–2004 → 2015–2024, on one axis (0 = many equal producers, 1 = a single producer). This is the most honest object on the page: it shows the two outliers doing the work instead of hiding them inside an average. The vertical tick is each group’s median.
The concentration average is two materials
The number that gets repeated is a group mean, and it says critical-material production grew more concentrated by +0.034. It is true, and it is misleading: two materials sit at the far edge of the distribution and carry the whole thing. Lithium’s HHI more than tripled (0.21 → 0.71) and cobalt’s tripled too (0.14 → 0.45). Remove those two and the average of the other 21 is essentially zero (−0.002).
| Critical materials | Mean change | Median change | Share that rose |
|---|---|---|---|
| All 23 | +0.034 | +0.046 | 15 / 23 |
| The other 21 (without Li & Co) | −0.002 | +0.044 | 13 / 21 |
The median does hold — most of the 23 rose a little — so a weak “typical material drifted up” claim survives for this set. But see the next section: it does not survive freezing the definition, so it is not a durable property of critical materials, it is a property of which materials the lists have come to include.
Freeze the definition, and the broad claim reverses
The lists were rewritten repeatedly between 2011 and 2023 — inside the change window — and materials were added partly because they had concentrated. Lithium, added to the EU list in 2020, is the clearest case. The clean test is to freeze the definition to the first EU critical-raw-materials list (2011), which sits at the end of the baseline decade: a material critical in 2011 cannot have been listed because of concentration seen after 2011. Seven of our materials were on that list. Run the same measure on just them:
| Critical materials | Median change | Share that rose |
|---|---|---|
| Full set (23, today’s lists) | +0.046 | 15 / 23 |
| Frozen to EU 2011 (7) antimony, cobalt, fluorspar, graphite, PGMs, rare earths, tungsten | −0.095 | 3 / 7 |
The materials critical before the window mostly diversified — antimony, graphite and rare earths came off near-monopoly highs, and PGMs eased from a lower base. So “critical minerals are concentrating” as a class statement is substantially an artifact of list expansion. What is left once selection is controlled for is not a class trend at all — it is the divergence: one material on that 2011 list, cobalt, concentrated hard, and it is the cleanest signal in the dataset.
The clean case, and the caveated one
Cobalt is the finding you can lean on. It was defined critical in 2011, before any of this; its production HHI tripled (0.14 → 0.45); and its reporting producers rose from 14 to 20 — so the concentration is real, not an artifact of fewer countries reporting. The mechanism is no mystery either: the baseline decade coincides with the collapse of Congo’s state producer during the 1996–2003 wars, and the rise since is Congo’s return and expansion to roughly 70% of world mine supply. Naming the cause does not soften the measurement — it explains it. Lithium is the one to be careful with. Its HHI rose more still (0.21 → 0.71), but it was listed only in 2020 (so selection bites), and its reporting producers fell from 10 to 7 — the one big mover where thinner reporting inflates the index. It belongs in the picture, labelled, not leaned on.
Every critical material, ranked production HHI change, 1995–2004 → 2015–2024
Does a control group help? A little, and it shows its own limit
The divergence above needs no control — each material is compared to its own past. But it is fair to ask whether ordinary commodities behaved differently. Most don’t make a clean comparison: bulky, low-value minerals (gypsum, salt, aggregates, talc) deconcentrate because they are produced next to where they are used — transport economics, not a counterfactual. The genuinely comparable non-critical commodities are the globally-traded, geology-sited ones. We first drew that set as three — gold, silver, potash — and an adversarial pass added a fourth we had missed: iron ore. Four is a check, not a control group, so each is shown by name:
And they split. Iron ore concentrated (+0.08 on broad coverage — the Australia–Brazil consolidation of the seaborne market); silver barely moved; gold and potash spread out. So the comparable non-criticals show no class trend either — which is this page’s point. “Critical vs ordinary” is not the axis that explains concentration; the mechanism inside each market is.