In a corporate web-design setup, who typically makes more per hour, the graphic designer or the programmer?

By graphic designer, I mean somebody who builds mockups probably in photoshop, selects font-styles, colors, etc. Most things layout-wise are near pixel-perfect, but likely after the initial implementation by the programmer, there will be a lot of small changes directed by the graphic designer.

By programmer, I mean somebody who is coding the CSS, the HTML, and light backend support, probably in PHP. The programmer will attempt to duplicate the mockups given the limitations of the medium, and consult with the graphic designer afterwards on what changes are tangible and which are not.

Both probably have an undergraduate degree from a respected four-year institution.