Income tax: Taxes levied on net income—that is, on gross income less certain deductions permitted by law. These taxes can be levied on individuals, corporations, or unincorporated businesses where the income is taxed distinctly from individual income.

Independent student: (See Financial dependency.)

Individuals with Disabilities Education Act (IDEA): IDEA is a federal law ensuring services to children with disabilities throughout the nation. IDEA governs how states and public agencies provide early intervention, special education and related services to more than 6.5 million eligible infants, toddlers, children, and youth with disabilities. Infants and toddlers with disabilities (birth–2) and their families receive early intervention services under IDEA Part C. Children and youth (ages 3–21) receive special education and related services under IDEA Part B.

Industrialized country or nation: A country or nation with a market economy comprising a significant portion of world production and trade markets.

Informal learning: Informal work-related adult education activities that take place without an instructor. Examples of such activities include on-the-job demonstrations by a supervisor or coworker; on-the-job mentoring or supervised training; self-paced study using books, videos, or computer-based software; attendance at brown-bag or informal presentations; and attendance at conferences, trade shows, or conventions related to one’s work or career.

Institutional support: The category of postsecondary education expenditures that includes day-to-day operational support for colleges, excluding expenditures for physical plant operations. Examples of institutional support include general administrative services, executive direction and planning, legal and fiscal operations, and community relations.

Instruction: This category includes expenditures of the colleges, schools, departments, and other instructional divisions of postsecondary education institutions and expenditures for departmental research and public service, which are not separately budgeted. Includes expenditures for both credit and noncredit activities. Excludes expenditures for academic administration where the primary function is administration (e.g., academic deans).

Instructional expenditures (elementary/secondary): Current expenditures for activities directly associated with the interaction between teachers and students. These include teacher salaries and benefits, supplies (such as textbooks), and purchased instructional services. (See also supplemental note 11.)

Instructional staff: Full-time-equivalent (FTE) number of positions, not the number of different individuals occupying the positions during the school year. In local schools, includes all public elementary and secondary (junior and senior high) day school positions that involve teaching or the improvement of teaching and learning. Includes consultants or supervisors of instruction, principals, teachers, guidance personnel, librarians, psychological personnel, and other instructional staff. Excludes administrative staff, attendance personnel, clerical personnel, and junior college staff.

Instructional time: Instructional time refers to the portion of the school day that is allocated to instruction. (See also Allocated time and Noninstructional time.)

International Baccalaureate (IB): A high school degree program internationally licensed by the International Baccalaureate Organization (IBO). The program placed a strong emphasis on the ideals of international understanding and responsible citizenship. The IBO offers schools three programs: the Diploma Programme for students in the final 2 years of secondary school, the Middle Years Programme for students ages 11–16, and the Primary Years Programme for students ages 3–12. Additional information can be found at http://www.ibo.org.

International Socioeconomic Index (ISEI): An index with a range from 0–90 used in the Program for International Student Assessment (PISA) to create a hierarchy of occupational status to equate the socioeconomic status of parents to student achievement.

Interpreting beyond text: A reading skill measured in the Early Childhood Longitudinal Study, Kindergarten Class of 1998 (ECLS–K). An example of this reading skill is making connections between problems in a narrative and similar life problems.