Divorce rate statistics are tricky to pin down, because they vary widely with region, the age of the marrieds, and the length of the marriage. According to census statistics, for example, marriages where one or both of the couple are under 20 years old have a whopping 85% divorce rate. However, marriages where a couple has been together for more than 25 years have less than a 10% divorce rate, and when the marriage lasts over 30 years, the numbers drop to less than 1%. Divorce rates also drop dramatically as people mature. The divorce rate of 21 and 22 year olds is double that of 24 and 25 year olds...just a few extra years of maturity makes a big difference.
Divorce rates have also been FALLING since the 1970's. While the national average is down about 2% since 1979, that number hides some interesting regional trends. In parts of the south, the midwest, and the rural areas of the western states, divorce rates have dropped by an average of 30% over the last few decades. These numbers are countered by urban divorce rates that have remained steady or risen slightly, but they demonstrate the amazing regionality of divorce numbers.
We also have to include a snippet about ethnicity here. Blacks, though statistically less likely to marry in the first place, are twice as likely to have a lifelong marriage than whites when they actually do settle down. Hispanic couples, probably due to the large number of devout Christians therein, are 30% more likely than whites to have a long, happy marriage.
Oh, and couples who go to church are 95% more likely to have a stable, long-term marriage. Even if the couple aren't particularly devout, the unifying experience of visiting church regularly and the availability of clergy to assist with marital problems makes those marriages far more likely to succeed.
So, the final numbers: A 19 year old, white, non-religious couple in a major urban area is looking at a 90+% chance of divorce the first time around. A black, Christian couple in their late 20's living in a rural area are looking at a sub-30% divorce rate. Your actual national average, nullifying both extremes, averaging the races and locations, and excluding remarriages, should end up in the lower 40% range. I've spent 30 minutes digging through studies, Census data, and NCHS research to compile this, but I'm not going to spend the hours needed to compile a more specific number for you :-)
Oh, and for the record: I am a 27 year old married man, with a 26 year old wife and two children. We've known each other since we were kids, and after half a lifetime of knowing each other and four years of marriage, no major problems have popped up. I thank God for her every day, and shake my head when I hear so many of my peers denigrating marriage or just assuming that it's "all about sex".