What is effective? Effective is that using less materials and costs to produce the most outputs.In the short run perspective a leader makes decisions all by himself and direct transmits that to the staffs,what seems like a efficient process, because it does not need time to discuss and to reach an agreement as well as  that also saves the organization costs. But what would happen during a long time for a firm? Can we still keep the advantage of costs?I would like to answer, no!  
Isolating others form firm's decision will reduce their enthusiasm and motivation to the job. In contrary to that, when a leader makes others feel they have been a part of decisions, people will have sense of belonging of the firms and they will be more active and initiative to work. A group decision can also avoid the one-sidedness problems which are frequently caused by autocratic decision.For example, the Ford was under deficit during 1980-1982 because of the compete against the japanese automobile manufacturer.Meanwhile the atmosphere in the company was also not optimistic and employees had many discontent emotions which leaded to several times strike. Since 1982 the company decided to introduce a new strategy that all employees should take part in the decisions and  encouraged employees to manage company by themselves. That brought ford a great success on changing the opposing relationship between company and employees and as well as a favourable turn to company's  income
.From this example, we can confirm that the sense of participation makes more efficient decision. Therefore a effective leader will try his best to do the right thing to the company,so he will make others feel they have been taken part in the decisions.