table(D$Variable)
Administrative levels
Area
Calendar
Communal buildings
Courts
Examination system
Full-time bureaucrats
Formal legal code
History
Indigenous coins
irrigation systems
Irrigation systems
Judges
Knowledge/information buildings
markets
Markets
Military levels
Philosophy
Phonetic alphabetic writing
Polity Population
Polity territory
Population of the largest settlement
Practical literature
Professional military officers
Professional soldiers
Professional priesthood
Religious levels
Religious literature
Roads
Script
Specialized government buildings
Settlement hierarchy
Written records