This report estimates the potential economic value of open data policies for Australia and the G20 countries. It finds that more vigorously pursuing open data policies could boost cumulative G20 GDP by around 1.1 percentage points over five years, more than half the G20's 2% growth target. For Australia specifically, open data is estimated to add around AUD 16 billion per year to the economy. Case studies show potential benefits across various G20 agenda items including trade, finance, fiscal policy, employment, energy and infrastructure. The report argues for strengthening existing open data initiatives and expanding the agenda to encourage more private sector data sharing while protecting privacy. International coordination on open data is seen as important for realizing its full economic opportunities.