Girls were left out of the original Millennium Development Goals (MDGs).
We're in the process of creating a Girl Declaration to ensure that mistake isn't repeated when the next set of development goals are decided in 2015, and today - on International Youth Day - we're stepping up our efforts even further.
At the heart of the Girl Declaration is the idea that women are girls first. In other words, if you want to empower women to contribute to developing economies, you have to reach them when they're girls.
The MDGs failed to do this. Not only was there no girl-specific goal but when we analysed the language used in the eight goals that were created, we found that the word 'girl' is not even in the top 100 words. 'Women' is used twice as many times.
The story of Barack Obama's election as US president demonstrates how important - and persuasive - using the right language can be.
For Obama this meant changing the phrase "yes it can be done" to the more inclusive and collective "yes we can". In development it means making girls a priority in the way we talk about alleviating poverty so that policy makers put them first in the way they tackle the issue.
If we can change the language then we can change the way people think, feel and act.
From the recent elections in Italy and Cambodia, where social media campaigning played a big role in changing the outcomes, to projects in the Philippines and Latvia, where it is being used to hold schools and officials to account - the growing influence of online conversations on policy making is clear.
That's why we relaunched the #VAWG (violence against women and girls) hashtag on Twitter as #VAGW (violence against girls and women) - to emphasise that changing gender norms around violence must start with girls.
Today we're doing the same thing with the #womenandgirls hashtag. From now on we'll be tweeting about issues affecting girls and women using the #girlsandwomen hashtag - giving girls their rightful place as the gatekeepers of a more gender-equal future.
Putting girls first
More than 300 people have tweeted using #VAGW since it launched. That's about 25 per cent as many as #VAWG, demonstrating that slowly but surely we're starting to change the way gender-based violence is debated.
At the moment, the number of people regularly tweeting about #womenandgirls is 30 times higher than #girlsandwomen. So, there's no better time to start changing that than on the UN's 14th International Youth Day - particularly as one of today's themes is girls and women.
By promoting girls to first place in the gender debate we can ensure that policy makers put their needs first too.
Will you join us?
Follow the #girlsandwomen conversation on Twitter
Find out more about the Girl Declaration