The rapid growth of program trading is due to three factors: first and foremost, the dramatic advances in technology, which allowed the speedier execution of trades via computers at the lowest cost...

The rapid growth of program trading is due to three factors: first and foremost, the dramatic advances in technology, which allowed the speedier execution of trades via computers at the lowest cost possible; second, the recognition that diversifying across stocks reduces risk; and third, the increasing sophistication of institutional investors in their trading activities and thus their need to be part of equity investments much more than before.