Gradient tool in Photoshop not even blend?

When you make a gradient in PS, for example a black to white gradient going across the screen, it seems that it is not an even blend from black to white. There is too much black, too much white, and not enough in between. Here is an example picture. The histogram display in the curves window shows what I mean. If it was an even blend, the histogram wouldn't show this curve shape. Am I correct in this? Is there a way to get an even blend?