The economy has grown by 4% per year over the past 30 years. During the same period, the labor force has grown by 1% per year and the quantity of physical capital has grown by 5% per year. Each 1% increase in physical capital per worker is estimated to increase productivity by 0.4%. Assume that human capital has not changed during the past 30 years. How much has growing physical capital per worker contributed as a percentage of total productivity growth