The Economics.api.dll is a managed assembly. It was written in a .NET language and compiled for the .NET platform. The error you get is due to the fact that regsvr32 is given you an error is that it was not made for managed assemblies. Regsvr32 is made for COM components and you got a managed assembly.
One question im thinking about is, why do you need to register it in the first place, this only makes sense if you have a solution where multiple applications need to share the same assembly (economics.api.dll). In other scenarios this should not be necessary to register the assembly.
If you do want to register the assembly the command for managed assemblies are "gacutil" and the documentation is found here:
http://msdn.microsoft.com/en-us/library ... 2c(v=vs.80).aspx
Hope this helps