Correction implies that an error was made, but this is really about optimality of approach. (dotearth.blogs.nytimes.com)
To put this more concretely, the principle of Pareto optimality tells us that we can not judge whether the addition of $ 1000 to the income of a family now receiving $ 10,000 annually is better than the same addition to a family now receiving $ 100,000 a year. (religion-online.org)
The other important condition that undermines optimality is when we see negative Sharpe ratios across the majority of portfolio building blocks. (ai-cio.com)