Photo courtesy of Tesla

Tesla Inc TSLA is replacing Apartment Investment and Management Co. AIV in the S&P 500 Index on Dec. 21, the index announced Friday. 

Tesla will also be added to the S&P 100, replacing Occidental Petroleum Corp. OXY; the energy company will remain in the S&P 500. 

It is estimated Tesla's addition will likely result in about $78 billion of inflows into the stock from passive funds indexed to the S&P 500 Index, according to Morgan Stanley analyst Boris Lerner.

After a long wait, Tesla has finally managed to receive S&P Global's blessings for addition to the Index.

Tesla will be the largest addition to the S&P 500 Index ever and will become the eighth most heavily weighted stock in the index.

S&P Makes Other Changes: In another index change, Apartment Income REIT Corp. NYSE AIRC will replace Dunkin' Brands Group Inc. (Nasdaq: DNKN) in the S&P MidCap 400.

Apartment Investment and Management is spinning off Apartment Income REIT in a transaction expected to be completed after the close Monday, Dec. 14, the index said, at which point Apartment Investment and Management will "no longer be representative of the S&P Composite 1500 indices market cap ranges."

Dunkin' Brands is being acquired by Inspire Brands in a tender offer set to expire on or around Tuesday, Dec. 15. 

AIV, TSLA Price Action: Apartment Investment & Management shares were down 4.88% at $38.60 in Friday's after-hours session. 

Tesla shares were down 0.24% at $608.50 after losing 2.72% in Friday's regular session and closing at $609.99.