How true self-assessment information can be?

In this week’s reading, we took a look at the Minnesota Council of Nonprofits Standards of Excellence. One of the ten principles raised my interest. It says that nonprofits should evaluate its actions and make self-assessment information public. I serious wonder if these kinds of information would be correct reflection of the organizations’ actions.
First, the nonprofit organizations might give unreal information to convince their donors that it is worth being funded continuously and to create a good image in the public. It might turn out to be exaggerating the positive impact they have made in the society and omitting the negative impact they have caused to the society. Although these evaluating organizations like the Minnesota Council says that they do not want the self-evaluation information from using their principles and standards to influence those donors’ decisions, it is impossible for those donors to totally avoid being influenced by those assessments when they are trying to pick an organization to fund. And it is the same case with the public because they might also make their decisions largely based on this information.
Second, different organizations may use different standards and principles to evaluate themselves. For those who use a low standard, although they didn’t perform well in the previous year, they may turn out to look fairly ok, while for those who use a high standard, although they did a good job on their mission, they may turn out to appear no better than those who didn’t perform as well.
I strongly believe that it is very important for the public to know how those nonprofit organizations are doing. However, do you believe that all the self-assessment information released from these organizations is fair and objective?