Falling assets under management quickly translates into lower fee income, and analysts have cut their earnings forecasts for Franklin's next financial year by 10 per cent since June, according to Bloomberg data.
Mr Hasenstab's $61 billion fund has lost 6 per cent so far this year, partly because his large holdings of Mexican bonds have tumbled with the value of the peso, a performance that puts it in the bottom one-fifth of funds in its category, according to Morningstar data.
Investors responded by pulling $1.9 billion in August alone. In all, outflows from the fund have totaled $6.4 billion in the past nine months.
Franklin has also been shedding assets in its global equities business, where funds under management are down 18 per cent year on year, according to a company update last week.
Half of Franklin's $806 billion in assets under management are in funds that invest wholly or mainly outside the US.
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Emerging markets have borne the brunt of worries about the economic slowdown in China and about what will happen when the Federal Reserve raises US interest rates.
Shares in the asset manager's parent company, Franklin Resources, are down almost 30 per cent so far this year, making it one of the worst performers in the sector, which has fallen only half as far.
The company declined to provide an executive for interview, but senior portfolio managers have repeatedly appealed to clients in recent weeks to stick with their investments.
Mark Mobius, executive chairman of the Templeton emerging markets group, wrote in a blog post on the August stock market swoon that "it is important to put these types of market corrections in context, remain calm and look for potential opportunities".
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Mr Hasenstab, meanwhile, said in a video message posted on the company's website that sell-offs in emerging market currencies had gone too far.
Christopher Harris, analyst at Wells Fargo Securities, cut his forecast for Franklin's earnings next year, and his share price target, by 10 per cent apiece in response to the latest assets under management figures.
But he added: "With so much negativity seemingly baked into the valuation at this point, we keep our 'outperform' rating on the stock even though there appear to be few near-term catalysts."