Final answer:
Since 1970, professional athletes' salaries have generally seen a dramatic increase in line with the growth of the sports industry.
Step-by-step explanation:
Since 1970, the salaries of professional athletes in aggregate have increased dramatically. This trend is reflective of the overall growth in the sports industry, which has seen significant increases in revenue due to factors such as television rights, endorsements, and consumer spending on sports. While there may be year-to-year fluctuations influenced by various factors, the long-term trend has been a substantial rise in average salaries for professional athletes.
According to the given information, the salaries of professional athletes have risen steadily since World War II. This suggests a continuous upward trend in salaries over time, indicating an increase in financial compensation for professional athletes.