With activist investors continuing to make headlines in the chemical industry, especially in the US, the struggles of Dow, DuPont and Botox producer Allergan are cases in point - the value of assets managed by activist hedge funds has surged six-fold in the past 10 years to $120 billion, according to a recently released study.

Although a tiny part of the $3 trillion hedge fund industry - including only about 165 such firms globally - the activists' often vocal criticism of company managements attracts publicity and can improve the share price performance of their targets, the report concludes.

The study by the Alternative Investment Management Association found that activist hedge funds on average hold a stock for about two years, compared with an equities market average globally of just three months. These funds are said to have returned nearly 14% in the three years to the end of 2014, more than twice the gains in the HFRI Fund-Weighted Composite Index.

Some of the world's most famous activist investors include billionaire William Ackman of Pershing Square - which lost its bid for Allergan to Actavis - and Daniel Loeb's Third Point Management, which is still hounding Dow.

In terms of share prices, activist hedge funds have also left a positive impact on listed companies with a 25% average improvement in the two years after the funds have sold out, the study said, without passing judgment on the toll the constant fights have taken on management and the workforce.