The 4 leading wirehouse firms are a significant part of most asset managers’ distribution strategies, according to a new report from Cerulli Associates, Boston.

Cerulli finds the top wirehouses–Merrill Lynch/Bank of America, Morgan Stanley Smith Barney, Wells Fargo/Wachovia and UBS–control nearly half of all advisor-managed assets. The firms together control about $3 trillion, or 80% of wirehouse assets.

Their size allows them to offer a broader array of services than most wirehouses can, and their network of external specialists make them ideal for investors with over $1 million in net worth, Cerulli says.