Marriage will make you happy, and money won't hurt.
But if you're seeking joy in your life it's probably best not to have children, a Harvard academic has told a Sydney conference.
The troika of experiences is conventionally considered to be the cornerstone of happiness, but such thinking does not stand up to scientific scrutiny, Harvard University psychology professor Daniel Gilbert says.
According to the scientific and economic research, only marriage proved to be a constant source of joy.
"Figures show that married people are in almost every way happier than unmarried people - whether they are single, divorced, cohabiting," he told the Happiness and its Causes conference at Darling Harbour.
"Married people live longer, married people earn more money per capita, married people have more sex and enjoy it more.
"Married people seem to be happier on every dimension that you can imagine."
Money, he said, could buy you happiness - just not as much happiness as people think.
"Money buys you a lot of happiness first and then it buys you less and less - every dollar buys you less happiness as the dollar before, and you reach a point where money is doing almost nothing for your happiness," he said.
"But it's never the case that more money makes you sadder. If you get millions and millions you never get depressed about it."
The happiness people gained from money was only relative, he said.
Having money only makes a difference if we have more money than the next person.
"If all of us double our income tomorrow we might as well have not have had an increase in income at all," he said.
Professor Gilbert left the sacred cow of parenthood for last, saying that despite the belief children were the apples of our eyes, they actually had a negative impact on happiness.
The more kids you have, the sadder you are likely to be, he said.
US and European studies over the past 10 to 15 years showed people's happiness did spike while they were expecting a baby, but it sharply plummeted after the child was born.
The nadir of people's happiness came when children reached the ages of 12-16, and only recovered when they had flown the coop, he said.
"In reality ... children do seem to increase happiness as long as you're expecting them, but as soon as you have them, trouble sets in," he said.
"People are extremely happy before they have children and then their happiness goes down, and it takes another big hit when kids reach adolescence.
When does it come back to it's original baseline? Oh, about the time the children grow up and go away."
Explaining why the statistics conflicted with most people's view of parenthood, Prof Gilbert made the unusual comparison to buying a pair of Armani socks.
"When people own Armani socks they can't stop telling you they are the best socks, the most amazing socks," he said.
"(But) I suspect that one of the reasons that people who own Armani socks think they are wonderful is because they have paid $US85 ($A90.30) for a pair.
"The psychologists tell us that we like things more when we pay for them - what does that sound like? It sounds like children.
"We pay for them in time, attention, blood, sweat and tears - what kind of idiots would we be to devote all of that to the rearing of our young if they'd didn't bring us some happiness?"
The fact that parenthood crowds out all other things in life could explain why we consider children as our greatest source of joy, he said.
"Parents tell me all the time that: 'My child is my greatest source of joy'," he said.
"My reply is that: 'Yes, when you have one source of joy, it's bound to be your greatest'.
The Happiness and its Causes conference runs today and tomorrow.
AAP