Adding complex data structure in mongoose

I have a set of data that I'd like to look like this:

{
   "city" : "new york",
   "state" : "missouri",
   "data" : {
       2012 : {
          volume : {
              cars : 12,
              trucks : 13,
              ...
          },
          price : {
              cars : 1234,
              trucks : 1343,
              ...
          }
       },                 
       2004 : { another year like 2012 },
       ...
    }
}

And here is my mongoose schema object:

var carMakerObject = mongoose.Schema({
    city : "string",
    state : "string",
    loc: { type: [Number], index: '2dsphere'},
    data: {
       2012 : {
         volume :  {type: Number, trim: true},
         price :  {type: Number, trim: true},
       }
       ...
    })

I guess my question is, how can I set up a complex data object that is an object with objects inside the object? I've played around with different syntaxes, but I'm missing something. I'm going to be adding even more data to this schema, and I'd like to keep it flexible and easily expandable.

Thanks!