This article originally appeared on Livemint.

Everyone knows of the Partition: a single, epochal event that created distinct identities memorialized everywhere—from atlases to history books. However, while Pakistan (including what is now Bangladesh) became a separate nation in 1947, what was left as India by no means homogenous. Language, culture, customs, practices, resources, opportunities, income and wealth varied widely across the country—best captured in economist Joan Robinson’s pithy statement: “Whatever you can rightly say about India, the opposite is also true.”

There was another partition, and it was different. It was undeclared and, many would say, an unintended consequence of central policies. It acquired an evocative but misunderstood label that is hard to lose despite trends to the contrary. This second partition cleaved India into two socioeconomic halves: one progressive and forward-looking; the other stagnating and stuck in the past.

Many labels were used to describe the other partition: a “vertical line through Kanpur”, the cow belt versus the rest and, perhaps the stickiest of them all, BIMARU states. The term, coined more than three decades ago by noted demographer and economic analyst Ashish Bose, clustered Bihar, Madhya Pradesh, Rajasthan and Uttar Pradesh together based on demographic indicators. Bose found that these states were contributing to the country’s population explosion as they held more than 40% of India’s population. The press adopted and, over time, morphed the term which came to imply acute economic underperformance and bleak prospects.

A host of reasons were advanced for the socioeconomic stupor: the resource curse, the freight equalization policy, an inability to break through regressive societal structures, etc.

Nikhil Prasad Ojha is a partner with Bain and Co. and the co-editor of the Mint-Bain series on 25 Years of Reforms. Parijat Ghosh is a partner with the firm and a member of Bain’s Healthcare and Industrial Goods and Services practices.