Evaluating the impact of the eParticipation services

In order to develop online services to meet the needs of young people (or another target group) the evaluation process needs to be done well. Sharing experiences about the evaluation of eParticipation services and the impact they have. How it's done well? What should be taken into consideration? How to measure the impact?

Background information:  In Finland there are online eParticipation services for all the citizens. One of the national services is Nuortenideat.fi  www.nuortenideat.fi (Young people's ideas) that was launched in 2015 in co-operation of Koordinaatti, the Ministry of Education and Culture and the Ministry of Justice involving young people and other stakeholders. Koordinaatti is in charge of the support services, development of the service, training and marketing of the eParticipation service. Evaluation of the service and the impact it's included in the work plan of Koordinaatti for the next year.