The manipulation of the primary trend is not possible. When large amounts of money are at stake, the temptation to manipulate is bound to be present. Speculators, specialists or anyone else involved in the markets could manipulate the prices, but it is not possible to manipulate the primary trend. Intraday, day-to-day and possibly even secondary movements could be prone to manipulation. These short movements, from a few hours to a few weeks, could be subject to manipulation by large institutions, speculators, breaking news or rumors. Individual shares could be manipulated, but manipulation usually end the same way: the security continues the primary trend. But it would be virtually impossible to manipulate the market as a whole. The market is simply too big for this to occur.
                                                                                    William Hamilton, the Dow theory