Questions and postings pertaining to the usage of ImageMagick regardless of the interface. This includes the command-line utilities, as well as the C and C++ APIs. Usage questions are like "How do I use ImageMagick to create drop shadows?".
The -scale option introduces new colors so one might expect an increase in size. You can fix by using -sample or by using -colors to reduce the number of colors in the image.
Are you using a modern version of ImageMagick, 5.5.7 or above? Older versions of ImageMagick did not compress GIF images because of the LZW compression patent.