Kenji and lucia are building their portfolios. kenji purchases shares in a mutual fund and pays fees to a manager who actively manages the mutual fund's portfolio. he does so because he believes that the manager can identify inexpensive stocks that will rise in value. lucia is not convinced. she buys shares in an index fund—a type of mutual fund that simply buys all of the stocks in a given stock index rather than actively managing a portfolio.

Google started as one of many internet search engines, amazon started as an online book seller, and ebay began as a site where people could sell used personal items in auctions. these firms have grown to be so large and dominant that they are facing antitrust scrutiny from competition regulators in the us and elsewhere. did these online giants grow by fairly beating competition, or did they use unfair advantages? are there any clouds on the horizon for these firms -- could they face diseconomies of scale or diseconomies of scope as they continue to grow? if so, what factors may limit their continued growth?