Reading historical commodity charts

Quick answer.

Read the chart labels first

Check the frequency, unit, currency, source and dates before you study the line.

An average is not a daily extreme

A monthly average cannot reveal the highest or lowest intraday trade in that month.

Indexing compares movement

Setting two series to 100 on one shared date compares percentage change across different price units.

A historical chart is a compressed description of a dataset. Before interpreting the shape, inspect the frequency, currency, unit and dates. A monthly chart cannot tell you the highest price reached during an individual trading day.

Average, close and intraday high

A monthly average combines observations across the month according to the publisher's methodology. A month-end close is a single observation. An intraday high is an extreme within a session. Those statistics can differ substantially during a volatile month. price-chart.com's World Bank history is monthly average data, and our table preserves that label.

Compare changes rather than dollar levels

A tonne of copper and an ounce of gold have different units and scales. In the comparison tool we index each series to 100 at the first shared date of the chosen interval. An index of 120 indicates a 20% increase from that starting observation. The common starting date prevents unequal periods from creating a misleading comparison.

Nominal is not inflation-adjusted

The source history is in nominal US dollars. A dollar price from decades ago does not represent the same purchasing power as a dollar price now. An inflation-adjusted chart requires a named inflation measure, its frequency and a chosen base period. Our price charts do not silently make that adjustment. When you want it, the real-price view in the Data Lab applies US CPI openly.

Missing values and changing coverage

Not every instrument has history starting at the same date. Missing observations should not become zero prices or fabricated interpolations. The comparison tool uses dates shared by its selected series and labels its calculation. CSV downloads contain the actual stored observations.

Use the historical archive to inspect the underlying table, then read the source notes before using the data in research. To compare up to six series with volatility and drawdown figures, open the commodity data workbench.

Test yourself. Check what you learned with the commodity data detective quiz: 5 quick questions, each with a short explanation.