This is discussing how many marriages last 30 years.
The national marriage rate for 1,000 people is 6.5 people per 1,000 total population.
And the divorce rate for 1,000 people is 0.9 people per 1,000 total population.
That means that for every 6.5 people that get married, 0.9 of those people are getting divorced.
The risk of divorce declines for each year of marriage.
The first 5 years have the highest number of divorces.
For example, the divorce rate in the first year is 1.9% (19 per 1,000).
Marriages that last 30 – 40 years have the lowest divorce rates.