Alan: One valid reason for the formal nullification of a Catholic marriage is "deliberate deceit (by either spouse) about some personal quality that can objectively and gravely perturb conjugal life." (Canon 108)
Given that most people -- especially most young people -- know neither themselves nor their motivations well enough to honestly represent their "being" to others (or to themselves), it is likely that most Catholic marriages are substantively invalid.
Declaration of Nullity
Conservatives Decry Pope Francis' Statement That "The Great Majority" Of Marriages Are Religiously Null