Build your own unit of value. Mix currencies, gold, bitcoin, housing and food — and watch what your unit would have done to the dollar over 20+ years, and what it does to your groceries.
One PUD buys the same world consumption basket, forever — named for the пуд, the 16.38 kg merchant weight that anchored eight centuries of trade. That is the official recipe; this laboratory hands you the ingredients — rebuild the unit your way and see if you can out-stabilize it. Same data as the live index; your weights.
Weights auto-balance to 100%. Set anything to zero to drop it.
Your PUD's dollar price is the weighted geometric mean of each component's USD cost — CPI×FX for currency areas, market price for assets — normalized to $1 at the window start. Purchasing power divides that by the world consumption price level W(t). Sources: FRED, OECD, BIS, IMF, S&P, Yahoo; monthly since 1999.
Gold-heavy mixes look glorious on the dollar chart — that's a growth chart. A unit of account needs the second chart flat: a ruler that stretches 8× is as broken as one that shrinks. Watch the wobble stat, not the altitude.
Some mixes edge out Classic on this specific window — usually by leaning on appraisal-smoothed housing data. Out of sample, structure beats fitting: the consumption-weighted basket is the mix that keeps working. The full argument is in methodology §M3.