how many couples in their 20s and 40s who were financially supported by their parents

How common is it for couples in their 20s-40s today to have been significantly assisted financially by their parents?

This isn't something folks run around bragging about so you never really hear about it. Is it 5% of couples or is it closer to 50%?

Stuff like paying college tuition, down payments for first house, new cars etc.