IVOO goes head-to-head with other plain-vanilla mid-cap offerings that track the popular S&P mid-cap 400, where constituent selection is at the discretion of the index committee and its weighting is based on float-adjusted market capitalization. The portfolio differs in market size allocation relative to other similar funds while the latter may include a significant share of large-caps and avoids small-caps, IVOO ignores large-caps entirely and devotes a chunk of its portfolio to small-caps. It also makes some significant sector bets.