A comparison of the two largest total bond market ETFs, Vanguard Total Bond Market ETF (BND) and iShares Core U.S. Aggregate Bond ETF (AGG), reveals that BND has held a narrow lead in total returns over the past decade, despite its expense ratio of 0.04% being one basis point higher than AGG's 0.03%. This slight edge for BND is attributed to its float-adjusted index, which excludes bonds held by the Federal Reserve, tilting its portfolio towards securities actively circulating in the market. Conversely, AGG, which tracks the standard Bloomberg U.S. Aggregate Bond Index, has shown a marginal lead in one-year total returns.