The International Telecommunications Union (ITU) and the Organization for Economic Cooperation and Development (OECD) provide Internet penetration statistics, which are collected from official national sources worldwide, and they are widely used to inform policymakers and researchers about the expansion of digital technologies. Nevertheless, these statistics are derived with methodologies, which are often opaque and inconsistent across countries. Even more, regimes may have incentives to misreport such statistics. In this work, we make a first attempt to evaluate the consistency of the ITU/OECD Internet penetration statistics with an alternative indicator of Internet penetration, which can be measured with a consistent methodology across countries and relies on public data. We compare, in particular, the ITU and OECD statistics with measurements of the used IPv4 address space across countries and find very high correlations ranging between 0.898 and 0.978 for all years between 2006 and 2010. We also observe that the level of consistency drops for less developed or less democratic countries. Besides, we show that measurements of the used IPv4 address space can serve as a more timely Internet penetration indicator with sub-national granularity, using two large developing countries as case studies.