Why is this relevant to the Vanguard Russell 2000 ETF? The Vanguard Russell 2000 ETF is a great portfolio option to add diversification. Investing in a small-cap ETF shouldn't replace the S&P 500 by any means, but some exposure is nice. Should you buy stock in Vanguard Russell 2000 ETF right now? Before you buy stock in Vanguard Russell 2000 ETF, consider this: