Net asset value growth at investment trust Aberforth Smaller Companies underperformed the company's benchmark in the third quarter, despite rising by 24.5%.Net asset value per share rose to 631.49p at the end of September from 512.77p, a tidy enough gain but slightly less in percentage terms than the 26.0% gain made by the Hoare Govett Smaller Companies Index (excluding investment companies), the index against which the trust measures its performance. The company's shares continue to trade at a discount to net asset value, and this discount widened during the third quarter from 8.9% at the end of June to 11.8% at the end of September.During the reporting period the level of gearing was reduced from 9.1% to 6%, the company said.An interim dividend of 6p has been declared in respect of the year to 31 December 2009.