Error in laravel query builder

My Laravel query builder return null:

    $country = DB::table('participate_company')

        ->join('company', 'company.company_id', '=', 'participate_company.company_id')
        ->join('country', 'country.country_id', '=', 'company', 'company.country_id')
        ->join('competition', 'competition.competition_id', '=', 'participate_company.competition_id')

        ->select('country.country_name', DB::raw('COUNT(company.country_id) as total'))
        ->groupBy('company.country_id')
        ->groupBy('country.country_name')
        ->get();

Table design:

1. Participate_company

competition_id (pk/fk)
company_id (pk/fk)

2. company

company_id (pk)
company_name
country_id (fk)

3. country

country_id (pk)
country_name

4. competition

competition_id (pk)
competition_year

I want to produce result of count distinct country based on competition year. For example competition year = 2012, country_name = England, count(total) = 20. But my current query produce null.

via Chebli Mohamed