The Green Report and the Farm Accountancy Data Network (FADN) are systems that measure the net farm income. Their aim is to show the economic situation of the Austrian agriculture. Hence, they serve as instruments that evaluate and assess the measures of domestic and Common Agricultural Policy. Comparing the results of the two systems reveal serious differences in the amounts of the indicators used. The analysis shows that these differences can be explained by elements of interferences. Sources of disturbance that deal with the different manner to select the holdings, increase the results in the FADN in comparison to the Green Report since the FADN concentrates solely on full-time farms that have an minimum economic size, higher than those considered in the Green Report. Moreover sources of disturbance exist, that can be traced back to different accountancy rules. These elements have an positive effect on the results in the Green Report compared to the FADN. As a whole the sources of disturbances concerned with the selection of the farms overweigh, which explains the higher assets and the higher net farm incomes in the FADN.