on the average

Actual experience shows that on the average the price of wheat and other nonperishable crops remains the same all year round except for an allowance for storage, interest and insurance charges.

实际经验，麦和其他不易腐烂的谷物的平均价格水平在一年之中是相同的，这还没有考虑必须的仓储、利息和保险费用。