NEW YORK ( TheStreet) -- A nearly 30% decline so far this year has gotten RadioShack ( RSH) kicked out of the S&P 500.

Standard & Poor's said in a press release late Thursday that Marathon Petroleum, a proposed spin-off of Marathon Oil ( MRO). Marathon Oil will remain in the S&P 500 after the spin-off.

RadioShack, whose $1.4 billion market capitalization is "more representative of the mid cap market space" according to S&P, will join the S&P Midcap 400, replacing Harte-Hanks ( HHS), which will move to the S&P Smallcap 600.

Harte-Hanks is pushing out Hutchinson Technology ( HTCH), which S&P said has the smallest market cap in the index.

Shares of RadioShack closed Thursday at $13.20, up 2%, on volume of 4.5 million, above the issue's trailing three-month daily average churn of 3.4 million. The stock is down 30% year-to-date, and 40% in the past year. Its 52-week low of $12.28 came on June 16.

Other changes include AMC Networks ( AMCXV) replacing Boyd Gaming ( BYD) in the S&P Midcap 400; Boyd Gaming moving to the S&P Smallcap 600 to replace StarTek ( SRT). AMC Networks is being spun off from Cablevision Systems ( CVC), which will remain in the S&P 500.

Also, Holly Corp. ( HOC) is replacing Frontier Oil ( FTO) in the S&P Midcap 400, as Holly is in the process of acquiring Frontier Oil. Entropic Communications ( ENTR) is replacing Holly Corp. in the S&P Smallcap 600.

All these index changes are expected to take place after the market close on June 30.

-- Written by Michael Baron in New York.

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