Apple Inc.'s profit margins are falling back to levels not seen since sales took off after the 2007 debut of the iPhone, as competition and lack of breakthrough products pressure the company to lower prices.

Concern over falling margins helped prompt a 33 percent decline in Apple shares from a record high of $705.07 on Sept. 21, making it the worst-performing stock in the Standard & Poor's 500 Index in the same period. Last week, Apple said the board and management are discussing the return of more money to shareholders, after a proposal by Greenlight Capital Inc.'s David Einhorn to pay out more of its $137.1 billion in cash and securities, possibly with higher-yielding preferred stock.

The latest quarter's drop in gross margin to 39 percent from 45 percent a year earlier was caused by the introduction of the iPad mini, other products with higher costs and price cuts for existing products, Apple said. Unless Chief Executive Officer Tim Cook unveils a revolutionary new gadget with premium pricing, Apple shares will remain under pressure.