Media buyers will have access to age and gender demographics for viewers and be able to calculate reach, frequency and gross ratings points.

The additional markets include Belgium, Brazil, Bulgaria, Czech Republic, Greece, Hong Kong, Hungary, India, Indonesia, Ireland, Israel, Malaysia, Mexico, Netherlands, New Zealand, Norway, Philippines, Poland, Puerto Rico, Singapore, South Africa, Spain, Taiwan, Thailand, Turkey and the United Arab Emirates.

In all, Nielsen will be measuring YouTube in 34 markets..
Here are all the countries affected by the Nielsen survey.