And now to start the call, I'd like to introduce our CEO, David Calhoun.
David L. Calhoun
Hi. Good morning, everyone. First slide. Absent currency translation, we had a very solid operating quarter. Revenue on a reported basis declined 1%; on a constant-currency basis, grew 4%. Adjusted EBITDA grew 1% on a reported basis and up 5% on a constant-currency basis. Margin expansion met expectations in every way and net debt leverage of 4x as we finished the quarter.
Growth and resilience were sort of apparent in what is clearly a more difficult macro environment. And for us, you see those implications in the developing markets, as well as the developed markets. Tangible progress in all our growth investments. High confidence. We'll talk about a few of those here in the upfront comments, and then we'll get more to it in Q&A I'm sure. And we are reaffirming our 2012 guidance.
With respect to the operating environment, strong growth in North America. For us, it has been robust, 7% on the buy side, which is, of course, sort of the bigger piece of the puzzle. And the Wal-Mart implementation went beautifully with very, very little lift in 2Q with respect to revenue in buy. So those are -- those days are ahead of us.
Difficult operating climate in western Europe, not news to anybody. Just to frame it, that is a little less than 15% of our overall revenue. Despite that tough environment, the resilience of our information business is always as apparent, and it continues to grow. Insights has been -- has declined quite a bit over 20%.
Solid growth in the developing markets, but not as robust as I would like. As you all know, we have a target of double digit. In the quarter, it grew 7%. Global multinationals are clearly being more selective. Believe it or not, I believe most of that is a reaction to difficulties in developed markets and just more selective resource calls.