You could come up with some loose measure for each of those. Genes: IQ, hard work: educational attainment, sacrifice: hours worked. Someone with ~110 IQ, colleg

You could come up with some loose measure for each of those. Genes: IQ, hard work: educational attainment, sacrifice: hours worked. Someone with ~110 IQ, college degree, and willing and able to work 60 hours a week is going to have an extremely high probability of achieving upper middle class. The biggest obstacle for that person is going to be health issues.