Difference is not automatically injustice
Different work, responsibilities, choices and risks may justify different rewards. The mere existence of unequal incomes does not prove that an economic system is unjust.
Basic needs establish a moral threshold
Inequality becomes difficult to defend when some possess extreme excess while others lack food, shelter, healthcare, safety or education.
Opportunity must be genuine
Formal equality means little when access to good schools, housing, healthcare and professional networks depends heavily upon family wealth.
Wealth can become political power
Large fortunes can influence lobbying, media, elections, employment and access to justice. Economic inequality then becomes inequality in political voice and legal protection.
The source of inequality matters
Differences arising from fair exchange differ morally from wealth produced through coercion, monopoly, discrimination, inherited privilege, exploitation or environmental damage.
Social mobility matters
Inequality may be less objectionable where people can realistically improve their situation. It becomes more entrenched when wealth and poverty pass predictably between generations.
No single ratio determines justice
The causes and consequences of inequality matter more than one numerical boundary. Access to essential services, political equality and social mobility must also be considered.
Evidence notes
Relevant evidence includes wealth concentration, wages, living costs, access to education and healthcare, social mobility, inheritance, taxation and the political influence of major wealth.
Ethical questions
How much inequality is compatible with equal citizenship?
Can extreme private wealth be justified while avoidable deprivation remains?
When does inheritance undermine fair opportunity?
Conclusion
Economic inequality becomes unjust when it arises from unfair conditions, prevents basic needs from being met, blocks genuine opportunity or gives wealth disproportionate control over society.