GDXJ is closely related to GDX, in name, exposure and history. The index covers global precious-metals-mining firms that generate at least 50% of their revenues from gold and silver. Junior gold miners are selected by market cap. It may include small- and midcap companies whose revenues are expected to grow as they further develop. To ensure diversification, single stocks are capped at 8%. Constituents are reviewed on a quarterly basis, where a sector-weighting cap factor is employed to ensure that 80% are determined as gold stocks, and silver stocks are limited to not go above 20%. The underlying index methodology has changed over time. In June of 2017, the index rules were modified, expanding exposure, to include larger companies.
