Does your chart show the actual salary paid to the worker or the total cost of hiring them? As workplace regulations increase so the costs associated with each member of staff rises, regardless of what their salary does.
ETA: it's also difficult to draw much in the way of conclusion from averages. Averages are pulled upwards by strong employees who produce more and earn more, and pulled downwards by deadbeat employees who produce little but play the system just enough to avoid getting fired. In much of Europe it can be hard to get rid of a bad worker (I don't know much about US employment laws) so you do get so-called zombie workers who do little beyond collecting their salary.
To give you a very simple example. As soon as I'm over the threshold to pay income tax, every £1000 salary I am paid results in approximately £660 in my pocket and costs the company more like £1200. (my share goes down once I move into a higher tax band). That's before the company deals with the expenses of administering payroll, workplace insurances, health and safty legislation, costs associated with providing workplace equipment etc.
It also overlooks the way that bosses often receive what's left of profits. If I own the company and hire you, you get a fixed salary and I get what's left. If the company struggles then I can't just impose a pay cut on you without your consent, so I take the hit myself. In exchange for that when times are good I take a bigger share. If you don't like it, start a company yourself so you take the bigger share when there is one.
It also overlooks the simple fact of the free market. If someone is willing to work for $7/hr why would anyone pay them more than that? If the worker is being paid $1.08 and thinks they are worth $1.80 it's for them to make the case why they should be paid more. If the boss thinks they should be paid more then the boss will pay them more. If they are readily replaceable by someone else who will work for $1.08 then their value is $1.08. It's the eternal divide between what something is worth to the buyer and what it's worth to the seller.
And of course ultimately it keeps coming back to the issue of who is responsible for looking out for me. Most of the arguments around "the company should pay more" boil down to little more than expecting Someone Else to watch out for me. If I'm in a strong position I may use that strength to negotiate a better deal. If I'm in a weak position I can whine all I want but it's nobody else's responsibility to pander to me just because I think they should.