Harry Markowitz' 1952 dissertation, 'Portfolio Selection' revolutionized modern finance creating MPT (modern portfolio theory). As useful as Markowitz' paradigm of mean-variance optimization is, what are shortcomings of the methodology in practice?

		Mean-variance optimization assumes that prior returns of assets are indicative of their future returns.
		Mean-variance optimization assume that the prior correlations between assets will hold into the future (for example, that A and B's correlation estimated over the prior period will hold into the next period).
		Mean-variance optimization assumes that all asset returns all perfectly normally distributed- when in fact, they are not.
		All of the above