It's essential to differentiate between normal self-interest and Narcissistic Personality Disorder (NPD). NPD is a clinical condition characterized by an inflated sense of self-importance, a constant need for admiration, and a lack of empathy for others. Only a small percentage of the population meets the criteria for NPD, estimated to be around 1-6% according to various studies.
On the other hand, most people do exhibit some level of self-interest or self-centeredness, which is a normal aspect of human nature. It is essential for self-preservation and personal growth. However, this does not necessarily mean that most people have a full-blown narcissistic personality disorder.
It's important to approach this topic with nuance and not generalize or stigmatize people based on specific traits. People's personalities and behaviors can vary significantly, and it's essential to recognize that everyone is unique in their own way.