http://www.encyclopedia-titanica.org/titanic-survivors/3rd class is 'Steerage'.
First and Second class are over-represented in the survivors, but lifeboats 8, 9, and 12-20 (19 and 20 not officially named so) contained 'steerage' class passengers.
"For some perspective, here is the price of tickets: First Class tickets ranged from £30 for a berth to £870 for a luxury suite with a private fifty-foot promenade. A Second Class ticket could be purchased for as little as £12. Steerage tickets ranged from £3 to £8. I have seen various estimates of how much that would be worth in current US dollars, but the cheapest ticket would have cost a clerk, typist, or shipyard worker a month's salary. The most expensive First Class ticket was similar in price to that of the most expensive luxury automobile."63% of first class survived, 43% of second class, and 25% of third class. Another way of looking at it, instead of a demographic, the same number of people survived from 2nd and 3rd class, at 172 and 171 respectively.