A Simple Look at Old vs New Sensex
When we compare the Sensex of 1986 with the Sensex of 2025, the change is very clear. Both years have 30 companies, but only six companies are common in both lists (see the image below).
This means most companies from 1986 are no longer part of the Sensex today. Either they shut down or they slowly moved out of the index.
Very Few Companies Stay for Long
From 1986 to 2025, many well-known names disappeared from the Sensex. This shows that staying in the index for a long time is not easy. Only a small number of companies were strong enough to remain part of the Sensex across many years. This itself tells an important story about how markets work.
The Sensex Works Like a Momentum Basket
The Sensex is not fixed forever. It works like a momentum portfolio. Companies that perform well and grow faster are kept inside the index. Companies that do not perform well are slowly removed. This keeps happening again and again over time.
Companies That Were Big in 1986
In 1986, the Sensex had companies like Indian Hotels, Tata Power, Hindustan Motors, Tata Motors, Bharat Forge, and many others. Along with them, some strong names like ITC, L&T, Tata Steel, Reliance, Mahindra, and Unilever were also present. Many of these old names later lost strength or relevance.
New Winners Entered by 2025
By 2025, many new companies became part of the Sensex. Companies like Infosys, Tech Mahindra, Axis Bank, Kotak Bank, SBI, and Indigo entered the index. These companies grew faster in recent years and showed strong performance, so they replaced weaker ones.
What This Teaches Us About Index Investing
This change proves one simple point. An index always moves with performance. It keeps winners inside and pushes losers out. Just like a momentum strategy, the Sensex keeps updating itself. Understanding this helps investors know why the index keeps changing and why performance matters the most.
