Estimated to be between 2 and 3 percent of the American population
The most important part of INFJs is their rich inner life, which is highly imaginative and capable of seeing unique possibilities everywhere. Often reserved and cautious children, INFJs may be reluctant to reveal their true and usually highly creative selves with others. Even then, they are selective about whom they risk sharing their ideas with, and they need to first make sure these special people are well known and deeply trusted. Quiet, gentle, and sensitive, INFJs like to watch first and join in after they feel comfortable and safe. They are rarely very assertive except as regards to their personal values, about which they can be quite forceful and passionate. Intellectually curious, especially about theories, global issues, and future possibilities, INFJs often have a unique vision about themselves and their projects. They are fiercely committed to their beliefs and can have surprising willpower to stay true to their view of how things should be. When challenged, they tend to dig their heels in more deeply rather than abandon or alter their vision to comply with what others think is best.
INFJs tend to love fantasy in their play and their stories. They often speak early and with a sophisticated style that belies their years. They usually like any creative activity, such as making things out of discarded objects, writing (especially creative writing in journals), dramatic play, reading, making or listening to music, and art projects or crafts. They may have imaginary friends or close friendships with their stuffed animals. Usually INFJs choose only a few, intimate friends and, while they are well liked for their warm and caring nature and respond with delight when invited to a friend's house, they are not typically the initiators of social activities. They tend to be highly empathetic and very nurturing with their friends, offering advice and expressing concern for others' safety and welfare. They have a strong need for harmony, especially in their treasured personal relationships, and can be deeply wounded by insensitive or cruel comments. They will go to great lengths to please the people they love and want to be appreciated for their thoughtfulness and their accomplishments. INFJs tend to idealize the people they love and seem to be on a constant quest to understand themselves and the meaning of everything that touches their lives.
Organized and efficient, INFJs are most comfortable with order, structure, and consistency. They are unnerved by constant or rapid change and need plenty of time, advance warning, and loving support to adjust to it. They like to be on time and prepared for all of their obligations, and they respect rules and authority. INFJs really like to be in control and can run the risk of being overly perfectionistic. They are frightened and stressed when too much changes too fast. Determined to stay in charge and unwilling to go against what they believe to be right, they can have real trouble compromising or backing down. Some time alone, or quiet companionship that reassures them they are supported and loved helps INFJs regain their sense of optimism and balance.
[Source: Nurture by Nature: Understand Your Child's Personality Type – And Become a Better Parent by Barbara Barron-Tieger and Paul D. Tieger]