Short answer: No. E.g. if you buy 'shares' in an index (via an ETF), you're effectively buying a weighted basket of the component shares in the index. If the in

Short answer: No. E.g. if you buy 'shares' in an index (via an ETF), you're effectively buying a weighted basket of the component shares in the index. If the individual shares are overpriced then so is the index as a whole. Hence the S&P500 has a price:earnings ratio, and you can decide for yourself if that ratio is looking 'toppy'.