Which voting system will reduce casteism in voting --- Preferential Voting System or TRVS = Two Round Voting System? (5-Dec-2015) No.1

December 5, 2015 No.1

https://www.facebook.com/mehtarahulc/posts/10153161426596922

Which voting system will reduce casteism in voting --- Preferential Voting System or TRVS = Two Round Voting System?
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Consider two voting systems ---- 
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(a) IRV = Instant Runoff Voting System = PVS = Preferential Voting System 
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(b) Two round voting system --- the first round is same as today, and the two highest vote fetchers are put in second round.
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Which voting system will reduce casteism in voting ? Or will they be almost same? 
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Please explain