I strongly disagree whith your opinion, but since I'm clearly outnumbered I'll accept your decision; in my opinion, the most information it's removed, the least useful this article becomes: the only “opening year” isn't really relevant, if it's taken individually - and despite being stable data, they're alike questionable (at least for early systems) - and this way even the sortability of the table   becomes pointless: it'll be more rational to revert the article to a mere, simple list as it was before March 2013 (if I correctly saw in the “history”). Conversely, the reader's usefulness of collecting statistic data in such a global list is far bigger than adding that to a nationwide/continental list: if you're interested in some specific system you can go directly to their individial Wiki pages, while if you aim to a world overview, it's somewhat tiring to “search, open & match” a handful of different article. Don't take it to heart, but I don't intend to further contribute to this list: good luck with your project, but from my personal point of view as reader/user it doesn't worth the needed time and effort.