Kim Jonker, a consultant to nonprofits, and William F. Meehan III, a senior director at McKinsey and Company, wrote in a classic article in the Stanford Social Innovation Review that mission statements that have the following characteristics are less likely to "creep":
1. They Are Focused
The best mission statements are not grandiose, but rather narrowly focused...more like a laser beam than a spotlight. Feeding all the hungry people in the world is laudable but likely out of reach for an organization with finite resources. The more focused the mission, the better the performance.
2. They Solve Unmet Public Needs
Nonprofits receive special tax status because they address problems that the government and business can't or won't deal with. Their mission statements must be about these public needs.
3. They Leverage Unique SkillsPassion and high aspirations are not enough for real impact. A nonprofit should have skills and be capable of specific actions that are different than other organizations. An example is Teach for America, which enlists young people (future leaders) to help eliminate educational inequality. That is specific as to the who and the what.
4. They Guide Decision MakingEvery nonprofit organization must make critical decisions and trade-offs...what intitiatives to proceed with and which to abandon. They should say "no" to funding opportunities or programs that do not align with their mission, but they should say "yes" to opportunities that will take their mission to the next level.
5. They Energize and Inspire Stakeholders.
A nonprofit has multiple stakeholders, often with conflicting interests and ideas. These can include board members, staff, customers, government agencies and the public. A great mission reflects all those interests but balances them, sometimes favoring some over others. But, as a result, the mission statement inspires those stakeholders.
6. They Anticipate Change
In anticipating change, these mission statements are timeless. To accomodate change, a nonprofit should re-explain its mission to its stakeholders every three to five years. This will regain their understanding and commitment. But that does not mean organizations need to change their missions. That should only be done in truly exceptional cases.
7. They Stick in the Memory
Stakeholders, especially external ones such as donors, rely on your nonprofit's mission statement to guide their actions. So the statement should be something that can be easily remembered. That means it should be short and concrete. A good example is Kiva's mission statement: "to connect people, through lending, to alleviate poverty."