The Indian stock market’s extreme reliance on just a single stock almost makes top-heavy U.S. equities look healthy.

A 164% surge in Reliance Industries Ltd NSE 1.08 %. -- India’s largest stock by market capitalization -- accounted for about 43% of the benchmark S&P BSE Sensex Index’s rally since equities bottomed on March 23. In comparison, the so-called FAANG stocks in the U.S. made up 22% of the S&P 500’s surge during the same period, according to data compiled by Bloomberg.

Owned by Asia’s richest man Mukesh Ambani, the oil-refining major has seen its market value nearly double to more  than $200 billion this year after a major push into digital and e-commerce ventures won it a flurry of investments with Facebook Inc., Google and other Silicon Valley giants. Reliance now has a 17% weighting on the Sensex index, up from 10% a year ago, and has propelled the measure up 50% since the March low.

The ballooning weighting of Reliance has also become a problem for the nation’s actively-managed funds as they hit a regulating limit for holding a single stock. This means money managers can’t add rising stocks, such as Reliance, and therefore risk trailing the market, according to Kotak Asset Management Co. Reliance’s shares were up 0.4% as of 12:32 p.m. in Mumbai.

Compared with India, the run up in American equities doesn’t appear as narrow. The U.S.’s largest stock, Apple Inc., contributed about 11% to the S&P 500’s jump since March as the iPhone maker’s market capitalization crossed $2 trillion. That’s followed by Microsoft Corp., Inc. and Facebook Inc. Netflix Inc. didn’t feature in the top 20 contributors, given its 0.7% weight in the benchmark. Gains appeared more evenly distributed for the European benchmark gauge.