Inequality is a subjective term. We can define it further with reference to specific context. Demographics or psychotropic concepts can help to discuss it in a specific frame of reference. For example, in India the concept of inequality is strongly rooted in economy and society equally.

Inequality on a global scale can be explained by different ways. There are arguments which go back to the origins of civilizations (i.e. based on differences in geographic factors, Jeffrey D. Sachs is one of the most well-known authors of the topic) where factors such as climate and closeness to seas influenced how societies evolved and the differences we observe nowadays are a consequence of the different paths experienced in different zones for millenia that have still not mixed up. Others trace the origins of inequality back to the institutions that emerged during the consolidation process of societies (see D. Acemoglu or the Institutionalist approach). Institutions oriented to exploit the resources of a country rather than investing in strong and inclusive production models cause those countries to never achieve sustainable growth based on "creative destruction".

There are other theories of economic growth & development which focus on the convergence/divergence of economies in the long-run rather than the origins of inequality. For example, one of the most known and studied models in economic growth (the neoclassical Solow growth model) talks about an eventual convergence of per-capita capital stock across economies. While interesting and applicable to certain cases such as US states or european countries, there has been a lot of discussion and critics to the neoclassical approach for long term growth when applied to different economies. Other theories which focus on endogenous growth can be related to the existence of human capital, which can be accumulated and combined with capital to deliver an ever-increasing output, therefore not converging as the Solow model would predict (this will depend however on the model and the assumptions taken). This models will usually make strong emphasis on the role of education and R&D public investment and on the effects of "learning by doing" processes or "learning spillovers".

Of course these are only a few examples of the many different theories and approaches for explaining long-run growth and inequality, but I think with them you can get some notion of the state of the arts: there is still not an absolute consensus on the origins of inequality and how to solve it. Based on the model one is taking into account, the solution might be to open up the country for foreign investments & trade, increase or reduce public spending, make a radical change in the institutions that run the country, increase or reduce taxes, rethink economic policies, or simply do nothing but leaving the private sector alone.

The answer is far from clear and from my perspective it will depend on the case one is observing. There is no such a thing as a one-size-fits-all when it comes to development and inequality.

The perpetual coexistence of developing countries (with high income inequality and poor standard of living) and developed countries (with low income inequality and high standard of living) can be explained under the following headings.

*1.Technological Advancement and Colonization.*

As a result of development of superior military and industrial technology, the Western Capitalist Powers were able to colonize less technologically advanced segments of the world. Thereby giving developed countries an edge in international trade

*2. Old International Division of Labour.*

Given colonization and technology advancement, trade between developed economies (Colonial masters) and developing countries (colonies) were based on old international division of labour in which developing countries specialize in exportation of primary products (and importation of manufactured goods) while developed countries specialize in exportation of manufactured goods (and importation of raw materials)

Developing economies dependence on primary exports implies little or no value addition which in turn inhibits job creation; development of infrastructure etc. These negative effects of dependence on primary export further worsen global inequality.

*3. Post Colonization and New International Division of Labour.*

After attainment of political independence from the colonial masters, one would expect the indigenous leaders of the erstwhile colonies to re-write their history and progress from dependence on primary export to manufactured export (new international division of labour).

However, the few elites in developing countries (for personal interest) chose to maintain the status quo at the expense of the masses. Consequently most developing countries only got political independence and not economic independence.

*Conclusion.*

Global inequality will persist until developing countries metamorphose from primary-export dependent economies to manufactured export dependent economies.

Interesting question and some very interesting posts. Equality and inequality, in their modern form, are 'concpeted' and conceived, most often than not, being based on an evolutionary process over the recent three centuries that have derived from a defined geographical area of the globe, with its inherent social, cultural, political, economic, natural resource and climate factors. This has provided for a conceptual 'form' of equality and inequality that has not enabled for a far more multiple diverse and divergent forms of equality and inequality conceptualization. An simplistic example of this can be provided in an exercise i used to provide to trainees in terms of active learning within Europe, Africa and the Middle East. The exercise was to provided to reflect on competition in the business, economic, social and cultural sense which clearly inferred to equality and inequality. The exercise was as follows: A basket of apples is placed under a tree, the first to get there owns the apples: what would you do? Most interestingly trainees form Europe would opt for hard competition, usually, but not always, i.e. who get the apples first owns than and can do what they like with them, including selling them to others, for example. This resulted in a win-lose model i.e. inequality. Trainees from Africa, most often, but not always, would opt for no competition and provided for a more collectivist view: all get to the apples together and share them among all. This resulted in a win-win model. Thus a focus on equality. Trainees from the middle east, usually, but not always would opt also for a collectivist approach, but with a slight twist, who got to the basket of apples first would share most of the apples, but not all. A win-lose-win-win model. A focus on equality, but also inequality. From this small and simple example it is clear that equality and inequality has rather differing points of view on what they actually mean and how societies across the globe perceive. Something which, i think, needs to be fully considered.

I read some of Branko Milanovic's works and these works gave me a sight. I can say that globalization can lower inequality global level. It was because of Far Asia countries had a chance to become more productive. Meanwhile, globalism raises inequality because the upper classes getting wealthier (especially in the global north). so globalism has caused 2 different effects on inequality.