During the 20th century alone, the population in the world has grown from 1.65 billion to 6 billion. In 1970, there were roughly half as many people in the world as there are now. Because of declining growth rates, it will now take over 200 years to double again.
This phenomenon is very common and manifests itself in the form of the condition known as Weak Erection - when the penis is engorged with blood but not to the extent that it is hard enough for pleasurable intercourse. A weak erection is caused by insufficient blood flow to the penile sponge-like tissues.
Note: Some drugs used to treat attention deficit hyperactivity disorder (ADHD)can cause long-lasting and sometimes painful erections. warnings: Misuse or abuse of methylphenidate can result in serious (possibly fatal) heart and blood pressure problems.