Data & methodology
Only observed monthly values are used. Missing observations are never interpolated or treated as zero. The default endpoint is the latest completed local month with all required series available. Each series has its own source, definition and verification time.
| Source | Unit | Definition | Coverage | Last checked |
|---|---|---|---|---|
| Hong Kong dollar M2 Official data | HKD million | End-month; not seasonally adjusted; HK-dollar M2 adjusted to include foreign-currency swap deposits; post-April 1997 definition | 1997-04 → 2026-06 | 8 Sept 2026, 5:49 am |
| Hong Kong headline CPI Official data | 2010=100 | Headline consumer price index; not seasonally adjusted; national series linked and rebased by BIS; restricted to 1997-04 onward | 1997-04 → 2026-07 | 8 Sept 2026, 5:45 am |
| HKD/USD Official data | HKD/USD | Monthly average of daily New York noon buying rates; not seasonally adjusted | 1981-01 → 2026-08 | 8 Sept 2026, 3:55 am |
| US M2 Official data | USD billion | Seasonally adjusted monthly money stock | 1959-01 → 2026-07 | 8 Sept 2026, 3:58 am |
| US CPI all items Official data | 1982-1984=100 | All urban consumers; all items; seasonally adjusted | 1947-01 → 2026-07 | 8 Sept 2026, 3:55 am |
| World Bank gold Official data | USD/troy oz | Monthly average; international benchmark, not retail | 1960-01 → 2026-08 | 8 Sept 2026, 3:55 am |
Why the results differ
M2 measures a stock of broad money. Scaling an amount by the M2 ratio preserves its mathematical share of that aggregate; it does not measure the cost of a household shopping basket.
CPI tracks the average price of a defined basket of goods and services. The result estimates an equivalent basket cost, not your personal cost of living. National baskets and money definitions differ.
US benchmarks first convert the starting amount into US dollars, apply the US M2 or CPI ratio, then convert at the ending exchange rate. Currency movements therefore affect the local-currency answer.
International gold is a monthly average in USD per troy ounce. Local price per gram = USD/oz × local currency per USD ÷ 31.1034768. Multiplying monthly averages is not the same as averaging daily converted prices. Retail premiums, taxes and fees are excluded.
These scenarios extend the observed monthly compound rate over the past 5, 10 or 20 years. They are conditional comparisons, not predictions or guaranteed investment returns. The choice of historical window and future exchange rate changes the result.
The Hong Kong dollar's linked exchange-rate system limits much of the currency effect against USD. Hong Kong and US M2 or CPI can still grow at different rates; a stable exchange rate does not make those benchmarks identical.
Formula
%p = (a−b) × 100
A × X₁ / X₀
(A / E₀) × X₁ / X₀ × E₁
Trend extension, not a forecast