If you don't own shares of BlackRock ( BLK), you've missed out on some significant upside in 2013. Shares of the $42 billion asset manager have rallied 19% so far year-to-date, doubling the broad market's performance over that same period. That rally makes a lot of sense -- to an investment manager, a broad stock rally means higher assets under management for BLK and, in turn, more revenue. In other words, we're in a very constructive market for BlackRock both fundamentally and technically. >>5 Hidden Earnings Bargains Worth Buying Now Bigger is better for asset managers, so BlackRock's position as the biggest investment manager in the world (with $3.8 trillion under management) gives it some big scale advantages. Much of that scale comes from the firm's 2009 acquisition of Barclays Global Investors, a move that fortuitously boosted BLK's equity exposure just a few months after stocks bottomed after the crash. Timing has proven to be everything at BlackRock, and that good timing continues to be worth watching now. Now BlackRock is working hard to grab more retail investors for its investment products. One big inroad comes from ETFs, which BlackRock offers under its iShares banner. The firm's decision to partner up with major retail brokers to offer commission-free ETFs should help spur an increase in retail AUM as Mr. Market plows onward and upward.