To compare broiler results from different flocks and different regions, the European Broiler Index (EBI) or European Production Efficiency Factor (EPEF) can be used.
This factor standarises technical results, taking into account feed conversion, mortality and daily gain
The formula is:  (Average grams gained/day X % survival rate )/Feed Conversion X 10
So with an average growth of 61 g (for instance an end weight of 2,257 kg in 37 days) and a survival rate of 96% (100 - 4% mortality) and a feed conversion of 1.62, the outcome would be:
(61 x 96) / (1,62 x 10) = 361 (361,5 to be exact)
The European Broiler Index compares technical results, but it doesnt automatically means that the results can also be compared economically.
If for instance a very low density is used during the grow-out period, the daily gain and with it the EBI will most likely go up, but the profit per square meter will go down, and the last one is economically of more interest.
If a low density, cheap feed is used, the daily growth and feed conversion might be negatively influenced, and with it the EBI, but the net profit per kg of meat might go up.