Each skill has its own skill level which is expressed as a percentage. Skill levels can be raised by spending skill points earned from gaining experience levels, or by reading specific books. As a skill's level increases, raising the skill further costs more skill points per percentage point. If statically (taking temporary effects aside, such as those of chems), the skill is at 99% or less, raising it (by 1 or 2 percentage points --- see below) costs 1 skill point; if the skill is at some value between 100% and 124% (inclusive), raising it (by 1 or 2 percentage points) costs 2 skill points; the full table of costs is: