Final answer:
Average farm size has remained consistent since 1987, despite economic pressures and urban development. Increased efficiency and productivity have likely played a role in maintaining this average farm size over time.
Step-by-step explanation:
Since 1987, the average size of farms has remained fairly consistent despite fluctuations in the agricultural landscape. While the specific average size from 1987 is not directly provided in the question, it is important to understand the changes and pressures that have shaped farming in the United States. Economic pressures and urban development have drastically reduced the number of small farms, and farmers, prompting increasing difficulties for new farmers to start. Meanwhile, farmland consumption by urban and suburban areas continues, adding to the complexity of maintaining farm size and productivity.
The historical context provided from 1940, where the average farm size was 174 acres with a standard deviation of 55 acres, can be compared to modern figures to reflect on changes over time. The number of farms has dropped significantly, but those that remain have become significantly more efficient. For instance, in the 1970s, one farm worker in the United States could produce enough food for 50 people, a number which has most likely increased since then due to technological advancements and improved farming practices.
Thus, while the exact average farm size in 1987 is not stated, the increased yield per hour of human labour and the overall trend towards larger, more productive farms likely compensates for the loss in small farms, keeping the average farm size relatively constant over the years.