Article: Some countries were not included for various reasons, mainly the unavailability of certain crucial data. The following United Nations Member States were not included in the 2010 report. Cuba lodged a formal protest at its lack of inclusion. The UNDP explained that Cuba had been excluded due to the lack of an "internationally reported figure for Cuba’s Gross National Income adjusted for Purchasing Power Parity". All other indicators for Cuba were available, and reported by the UNDP, but the lack of one indicator meant that no ranking could be attributed to the country. The situation has been addressed and, in later years, Cuba has ranked as a High Human Development country.

Question: What is the main reason that countries were excluded from the 2010 report?
unavailability of certain crucial data