Dietary intake of the times

Estimates of salt intake in the United States are harder to find, so we have to look to novel sources for clues. For example, army rations are a relatively stable reflection of the dietary intake of the times— and army rations suggest that salt intake likely declined by about 50 percent from the early 1800s to 1950.

Does it say that the rations of salt in the army reflect pretty well how much salt was eaten in the past (of the times)?