Simple economics: India would've incurred a huge cost by joining RCEP

Now, RCEP will incur the costs of losing the Indian market which was the only worthwhile market

India’s decision not to join RCEP has pleased some people and annoyed others. None of these people, however, are using basic economics as a reason for their reaction. 

There is a very simple condition laid down in economics. It’s called the Heckscher-Ohlin Theorem. It says that trade between countries depends on what David Ricardo, a very influential English economist in the 19th century, had called competitive advantage.  

He meant that countries export products that use their “abundant and cheap factors of production, and import products that use the countries' scarce factors.” 

In India, the abundant factors are labour and land.