How the AMPI is built

We compute an Artist Price (AP) for each artist from auction hammer prices at leading houses, using a rolling 24-month window with date-sensitive weights that emphasise recent sales. We then form the index by summing APs (up to the first 10,000) and comparing that sum to a base period; the full history is exponentially smoothed to reduce noise. A Core variant (AMPC) includes only artists with ≥30 sales in two years. Figures are recorded net of buyer’s premium and converted to GBP using the Bank of England rate on the sale day (see AMPI white paper).