Scepticism among politicians is not born only of spite. Governments invest in higher education to boost productivity by increasing human capital. But even as universities have boomed, productivity growth in the rich-country economies has fallen. Many politicians suspect that universities are not teaching the right subjects, and are producing more graduates than labour markets need. Small wonder that the state is beginning to pull back. In America government spending on universities has been flat in recent years; in Australia, even as the price of humanities degrees doubles, so it will fall for subjects the government deems good for growth.
If "so" is a conjunction, does that mean this sentence is a grammatically wrong as there is no main clause? And if not, what does "so" mean here?