PARIS, Oct 8 (Reuters) - A global deal to ensure big companies pay a minimum tax rate of 15% and make it harder for them to avoid taxation has been agreed by 136 nations, the Organisation for Economic Cooperation and Development said on Friday. The OECD said four countries - Kenya, Nigeria, Pakistan and Sri Lanka - had not joined the agreement. Also read: Big investment hubs dodge a bullet in global tax overhaul "Today"s agreement will make our international tax arrangements fairer and work better," OECD Secretary-General Mathias Cormann said in a statement. "This is a major victory for effective and balanced multilateralism." The OECD said that the minimum rate would see countries collect around $150 billion in new revenues annually while taxing rights on more than $125 billion of profit would be shifted to countries where big multinationals earn their income.