ISTJ - Introvert, Sensing, Thinking, Judging.
ISTJs are responsible organizers, driven to create and enforce order within systems and institutions. They are neat and orderly, inside and out, and tend to have a procedure for everything they do. Reliable and dutiful, ISTJs want to uphold tradition and follow regulations.
ISTJs are strong-willed and dutiful, very responsible, calm and practical, they create and enforce order, and they are a jack-of-all-trades. They are also stubborn, insensitive, always by the book, judgemental and they often unreasonably blame themselves.
In the population, 11.6% of them are ISTJ, making them the third most common type in the world. They are also the most common among men which are 16.4% comparing to 6.9% being women.