I'm trying to work with Google charts API, but I get an error I can't understand:

Here is my code:

<script type=text/javascript src=https://www.google.com/jsapi></script>

<script type=text/javascript src=js/statistics/overview.js></script>

And the code from overview.js is like this:

var statisticsOverview = {

    init: function() {

        google.load(visualization, 1, {packages: [corechart]});

        google.setOnLoadCallback(this.drawIncomeChart());

        google.setOnLoadCallback(this.drawExpensesChart());

        google.setOnLoadCallback(this.drawEconomiesChart());

    },

    drawIncomeChart: function() {

        var data = [

            ['Year', 'Income'],

            ['October 2013', 1000],

            ['January 2014', 1170],

            ['March 2014', 660]

        ];

        var options = {

            title: 'Income Performance',

            colors: ['green']

        };

        var id = 'chart_income';



        this.drawLineChart(data, options, id);

    },

    drawExpensesChart: function() {

        var data = [

            ['Year', 'Expense'],

            ['October 2013', 1000],

            ['January 2014', 1170],

            ['March 2014', 660]

        ];

        var options = {

            title: 'Expense Performance',

            colors: ['red']

        };

        var id = 'chart_expenses';

        this.drawLineChart(data, options, id);

    },

    drawEconomiesChart: function() {

        var data = [

            ['Year', 'Savings'],

            ['2004', 1000],

            ['2005', 1170],

            ['2006', 660],

            ['2007', 1030]

        ];



        var options = {

            title: 'Savings Performance',

            colors: ['orange']

        };



        var id = 'chart_economies';

        this.drawLineChart(data, options, id);

    },

    drawLineChart: function(data, options, id) {

        console.log(google.visualization);

        var chartData = google.visualization.arrayToDataTable(data);



        var chart = new google.visualization.LineChart(document.getElementById(id));

        chart.draw(chartData, options);

    }

};



statisticsOverview.init();

This is strange, because console.log() will give me the google object with the property visualization. What am I doing wrong?