If July is any indication, the whole is worth less than the sum of its parts, at least when it comes to Cablevision Systems and AMC Networks. System operator Cablevision spun off AMC, home of “Mad Men” and “Breaking Bad,” to shareholders at the end of June 2011.

At the time, the company made the usual statements about how splitting apart the operations would allow each business to flourish. Last month, that seemed to come true, at least as far as investors were concerned.

According to figures compiled by S&P Dow Jones Indices, Cablevision was the 10th-best performer in July among the large-capitalization stocks in the S&P 500. The cabler’s stock gained 15.43% during the month, as Bank of America/Merrill Lynch upgraded the shares to “buy” and rumors again circulated that the company would be bought out.

AMC, whose nets include IFC, Sundance and WE tv, continued to benefit from the popularity of its original programming. The stock, a component of the S&P MidCap 400 index, was that benchmark’s sixth-best performer in July. For the month, it rose 21.97% and is within striking distance of its 52-week high.

The only other showbiz stock among July’s big movers was Netflix, which fell 16.97% for the month (the 13th-worst performer in the S&P 500) on continued profit concerns.