There are several ways to measure development levels and the gap between developed and developing countries:
1) GDP and GNP per capita are traditional economic measures but don't capture inequalities within countries.
2) Social indicators like health, education, and housing provide a more holistic view of development.
3) Composite indices that combine economic and social factors, such as the Human Development Index, provide a comprehensive overview of development levels.
4) Other indices measure specific issues like the digital divide, gender inequality, and livability between countries. No single measure can fully capture a country's development status.