According to [1], it (cement) has been around ~70 megatonnes in each of those years, while the same site agrees with the article and puts China at around ~2 gigatonnes for each of those years.

Usage in the U.S. took a nosedive in 2008, I assume because of the recession. Pre-2008 shows a local maximum in 2005 of 128 megatonnes; so still an order of magnitude less.

[1] http://www.statista.com/statistics/273367/consumption-of-cem...

cement and concrete are different materials

If you want to be real careful you should say Portland cement.

(because, for instance, the bitumen in asphalt roads is also a cement)

But you need cement to make concrete.

Yes, but if you're comparing usage across countries you probably want to compare the same thing; either concrete or cement.

Indeed but if you want a pretty good estimate you can just whatever mixing factor is most common in China or the US and convert :)

For anyone else that's curious, cement is mixed with water and some sort of aggregate to make concrete.

Don't forget the sand, which is technically an aggregate[1]. Using the wrong sand is a classic mistake being rediscovered in China:

http://www.wired.com/2013/03/poor-quality-chinese-concrete-c...

[1]-The concrete recipes I remember always had sand and rocks, gravel and/or pebbles (depending on local availability)

Yes, you want coarsely crushed ('sharp') sand, not sand that has better decorative qualities.