Ember.computer.sort doesn't seem to work

I have a template like so:

{{#each rate in package.ratesSorted}}
  {{rate.year}}
{{/each}}

I want the rates to be sorted by ascending year, so I have:

 var Package = DS.Model.extend({
  rates: DS.hasMany('rate'),
  ratesSorted: Ember.computed.sort('rates', (a, b) => {
    return a.get('year') > b.get('year');
  })
});

Package.reopenClass({
  FIXTURES: [
    {id: 1, rates: [1, 3, 4]}
  ]
});

And my rate Model looks like this:

var Rate = DS.Model.extend({
  year: DS.attr('number'),
});

Rate.reopenClass({
  FIXTURES: [
    {id: 4, year: 4},
    {id: 1, year: 1},
    {id: 3, year: 3}
  ]
});

But it then ends up being sorted 3,4,1. Why?