The index that the US 30 is based on is often criticised for being unrepresentative of the US economy, since it only measures a small number of companies. It’s also share price-weighted, meaning that potentially overvalued stocks may have more of an influence on its performance. Some investors instead prefer to trade on our US SPX 500 – Cash instrument, which is based on another major index measuring 500 of the biggest market cap companies, as this may provide a more rounded overview of the US economy.