With Joe Biden and Bernie Sanders now poised to duke it out for the Democratic nomination following Super Tuesday, both should be focused on ways to reduce inequality in the labor market.

The "Fight for $15" movement for a higher minimum wage is a very good start, and I'm glad to see both the candidates support that campaign. But they should be looking at other ways to address systematic problems in the labor market, including how hard it is for caregiving service providers to keep pace with workers engaged in the manufacture and distribution of goods.

To illustrate one of these problems, let's look at the prospects for two sets of workers employed in transportation services: truck drivers and bus drivers. Truck drivers haul cargo. Bus drivers transport people. Both will be significantly affected when self-driving vehicle technology advances from beta-stage to full-blown acceptance. But the prospects for future employment could be quite different.

Most of the jobs for truck "drivers" will probably go away, with a much smaller number of truck "operators" left on the job. Perhaps one operator for a convoy of 10 trucks, all electronically linked together as they roll down the highway. Or maybe one operator, sitting at a workstation with several video monitors, directing the travel for a whole fleet of in-town delivery vehicles. Under these scenarios, there will be far fewer truck operators that there were truck drivers, but with each multi-truck operator far more productive than each single-truck driver, they have the potential for very good earnings.

But the future could be quite different for bus drivers. Focusing on school buses, parents will not want their children left unattended, so most of the school bus "drivers" will be retained (and retrained) as school bus "monitors." The duty of the monitor is to keep the kids safe and under control on trips to and from school. The school bus drivers may not lose their jobs, but with no gain in productivity, they have a slim chance of keeping up their earnings compared with the multivehicle truck operators.

Other jobs in the service sector will face the same daunting problem of low to no productivity growth, and therefore few prospects for larger paychecks. Two of the fastest-growing professions, according to the U.S. Department of Labor, are home health aides and personal care aides. These high-skilled, low-paid jobs are already at the bottom of the pay scale, and with one-to-one personal care, we really don't want these caregivers to be more productive. (We don't want them racing through their visit to our mom or dad!) What we do want is for them to go about their work with great competence and compassion.

I believe it's time to consider a new model for compensating many workers in the service sector, especially those engaged in caregiving work. This model would better reflect the value society places on their services. There are roughly 500,000 school bus drivers nationwide earning a median wage of around $16 an hour. There are more than 3 million home health aides and personal care aides nationwide earning a median wage under $12 an hour. The federal government should step in and supplement their wages with a $10-an-hour Earned Income Credit. The EIC would be added to their regular salaries and paid to these workers week-by-week as it is earned.

We should do this because we recognize how important these caregiving services are to us and our families. We acknowledge that small-business owners who employ caregivers often find themselves at an economic disadvantage, and that this wage supplement would help them recruit the best workers for these caregiving positions. And we understand what a great boost it would be for the economy to add around $70 billion of purchasing power to the workers and families in these lower-paid professions.

I would love to see Biden, Sanders and progressives everywhere get behind a plan like this to address inequity and inefficiency in the labor market. (The candidates should be looking for something beyond "Dump Trump" to excite the voting public.) I believe this would put them on the right track.

John Crea, of St. Paul, is the author of "Recalibrating the Labor Market."