why a portfolio should have negative covariance do negative correlation reduce risk why is portfolio risk reduced by positive covariance? why does portfolio risk decrease why has a negative covariance when portfolio risk is reduced why a portfolio should reduce risk does portfolio risk increase cov why have covariance why is portfolio risk a good risk factor? why should portfolio risk be negative why is portfolio risk important why should we choose portfolio covariance to be negative? what does negative covariance mean for portfolio risk why is there a risk of negative correlation in portfolio risk why should a portfolio be negatively correlated why a negative covariance reduces portfolio risk why is portfolio risk negatively correlated what is negative covariance? why is a covariance negative