Good question actually!

I guess there are two main "school of though" when it comes to "scale":

1. It only has potential to "scale" when it is more or less self-replicating, i.e. gets taken up by companies without much outside intervention and a market demand is either already there or starts to exists due to the improvements on the supply side.

2. It only has potential to "scale" when it can be implemented by large scale government structures (or large grass-roots organisations) with little top-level intervention or many qualified staff.

I guess in theory the first one is better (but not always applicable) while the second one is sort of the minimum goal (and often what institutional donors mean with "scale").

A quick search of the word 'Scale' on this Susana site reveals 10 pages of documents or comments where this over used word is mentioned, but in all this mass of information, I could not find one concise definition. Perhaps I didn't search hard enough. There is a general consensus within the sector that we have to achieve scale to address the needs of the 2.4 million, but without a clear understanding of what 'scale' means and what it looks like when we get there, our chances of reaching it are pretty slim. Without a definition we are in danger of lacking direction. We often talk about 'Working at Scale' , 'Scaling-up' and 'Going to Scale' and donors love using the phase 'Pilots never fail and never scale' without actually telling us what it means. Some academics would even say that if a term cannot be defined; it cannot exist.

There is a strong argument that if a sanitation initiative has no potential to scale; don't bother even starting, so answering this question is very important. Water For People has real ambitions for scale in all the countries where works and has developed a definition which attempts to be equally applicable to Kolkata slums as the sparsely populated areas of the Bolivian Alto. BIG NUMBERS are a pretty meaningless and an un-useful method of comparison. Does anybody else have a definition of 'Scale' ? Good or Bad? or has anyone else tried to tackle tying down this elusive term?