Two 20 hour jobs is optimistic. Part-time is considered anything under 35 hours a week. It's much more likely you're going to be stuck trying to squeeze two 30 hour jobs into a single week because neither job is going to consider the schedule of the other and you're going to be caught in between. And as others have said, neither jobs are going to give you the benefits a 40 hour job should be giving you, but are often screwing you out of because, in the US, pretty much nothing but cheap healthcare is guaranteed for 40 hours now.

It’s rarely two 9-5 M-F jobs that add up to 40 hours a week.

It’s usually a combination of a primary job that is just below the threshold of full time and therefore doesn’t qualify for basic benefits like health insurance, paid time off, or retirement <32 hours.

Usually the second job is in the evening and weekends. Service jobs, retail, etc. Often the schedule varies wildly and changes often.

Typically both jobs are paid hourly and can end at any time.

A lot of people work much more than 40 hours per week, but don’t have the security of a full time, salaried job.

Most places don't offer benefits under 36-40 hours, including 401k, IRA, other retirement options. Most part time jobs are lower pay. And also if you are driving 15-30 minutes to either job, that ends up being like 2 hours total drive time since we are a car congestion-centric culture. Working multiple jobs just to get by is predatory and aimed at the extremely poor people.

I think there are benefits when you work a 40 hour job, which you don't get when you work 2 20 hour jobs.

Edit, here is a random website I found that says the same

Edit 2: not to mention I think its likely that 20 hour jobs are paid worse than 40 hour

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