A marquee offering from the world’s biggest hedge fund manager, Bridgewater Associates, had its worst month in two years in August, prompting the firm to defend its approach as a solid strategy in good markets and bad.

The $70 billion All Weather fund is down nearly 5% for 2015 through mid-September, and its assets have dropped by more than $8 billion since the start of the year, as clients have shifted money from the fund into another that makes more traditional hedge fund wagers, according to a person familiar with the firm.