You mean "half".
In engineering theory the 2 stroke has about 60% more power (not 100% because some part of the pistons travel is used for gas exchange).
But with modern emission limits the 2 stroke can't reach 60% and may even became less powerful than the 4 stroke. In car engine technology with Euro 6 on the horizon we might never see a 2 stroke again.
Corrected.
Btw. a few years ago the breaking news all over the place was that the future is in very sophisticated 2-stroke turbo engines for cars and motorcycles?!?
Now they produce turbo charged gasoline BMWs that have kerb weight of 1400+ kg, 200 hp and consume 9 l of gasoline on the average, the same as my car that weighs 1150 kg, has 1400 cc naturally aspirated engine with 110 hp. If somebody told me that 15 years ago when turbo charged cars with 150-200 hp consumed 15-18 l/100 km, I would say that kind of engineering will never exist.
Of course it is not possible (or economical) to make clean 2-stroke engines for cars and motorcycles.
Sometimes we from Europe and USA are very westerncentric-eurocentric - there are a lot of places in the world that do not adhere to Euro emission norms and never will.