That statistic was bogus. It was taken by dividing the marriage rate in a year by the divorce rate in the same year. Well you instantly see the problem. In a single year, the couples getting married and the couples getting divorced are not one in the same. And the statistic happened to be taken in a year when a large generation was entering prime divorce years and a smaller generation was entering prime marriage years. Even then it wasn't 50%. It's just that if the trend held, it would get to 50%. Which of course it never did because it was a function of how it was taken and of generation size.
Measured properly, IE looking at the percentage of Marriages of a time period years later to see if they divorced, the divorce rate was about 35% when the media screamed it was 50% OH NOES!!! and it has been falling. For marriages initiated between 2000 and 2010 it appears that about 80% will make it to their 15th year.