That's the Vanguard Emerging Markets Stock Index Fund and indeed I own some of that. However it's a relatively small part of my portfolio. The risk and variance are much higher, and the risk and variance of a single country index fund would be higher still. This fund dropped more than 75% during the 2008 crash and still hasn't recovered. The expense ratio ranges from about 0.2% to 0.33%, higher though not hugely so than domestic and total international index funds.

Most investors, especially those with smaller portfolios or who have a shorter time horizon, are probably better off with something like the Vanguard Total International Stock Index Fund which includes a developing markets component, but also includes Asia and Europe, or the Vanguard Total World Stock Index which adds the United States to the mix.