Knowing your desired rate of return is simple enough, but whether you can reasonably achieve that rate of returnor tolerate the necessary risk is another story.
The dispersion is somewhat larger when measuring average annual returns (annualized return, recall, is the compounded or geometric rate of return during a multiple-year time period).
Three years ago the Bank of Cyprus also bought large quantities of Greek bonds, largely for reasons unconnected with their rate of returnor risk, to help out Greece.