Final answer:
The proportion of stocks in the S&P 500 index with negative earnings last year can be calculated by dividing the number of companies with negative earnings by the total number of companies and multiplying by 100.
Step-by-step explanation:
The proportion of all stocks in the S&P 500 index that had negative earnings last year can be calculated by analyzing the financial statements of each company included in the index. By looking at the net income figure reported in each company's income statement, we can determine if the earnings were positive or negative. The percentage of stocks with negative earnings can then be calculated by dividing the number of companies with negative earnings by the total number of companies in the index and multiplying by 100.
For example, if there are 500 companies in the S&P 500 index and 50 of them had negative earnings last year, the proportion would be:
50/500 x 100 = 10%
Therefore, the proportion of stocks in the S&P 500 index that had negative earnings last year is 10%.