Literal translation
One year in the other.
Meaning
one year with another, on average
Explanation
This formula is used to indicate an average calculated over several years, particularly in agricultural matters where harvests, income, or prices vary greatly from year to year. Saying un an dins l'autre, one year in the other, treats good and bad years as offsetting each other, blending together, to arrive at a figure or an assessment representative of the whole stretch of time. The image is one of mixing, the idea that one year pours into the next and dissolves there, a richer image than a simple addition followed by division. It corresponds exactly to the equivalent French expression bon an, mal an, sharing the same function, one stressing the blending of years, the other the alternation of good and bad. It is used in ordinary register, especially in economic or agricultural contexts, to present an average figure without dwelling on the yearly variations that produced it.