Why doesn't Monkey generate the same sequence of events?

I'm running stress tests on Android using Monkey to generate the workload. For the type of analysis I have to do, I need to generate the same sequence of events for each experiment. So, in every experiment, I always use the adb shell monkey command with the same seed. For instance: while true; do adb shell monkey -p com.android.chrome -s 1 --pct-appswitch 100 --ignore-crashes --ignore-timeouts --ignore-security-exceptions --monitor-native-crashes -v -v 1 sleep 1 adb shell monkey -p com.facebook.katana -s 1 --pct-appswitch 100 --ignore-crashes --ignore-timeouts --ignore-security-exceptions --monitor-native-crashes -v -v 1 sleep 1 adb shell monkey -p com.google.android.apps.maps -s 1 --pct-appswitch 100 --ignore-crashes --ignore-timeouts --ignore-security-exceptions --monitor-native-crashes -v -v 1 done The applications I launch are ten in total. However, looking at the measurement data, it seems to me that the system is stressed differently with each run. In particular, I find that the average launch time of applications degrades to a different extent in each experiment. Is everything normal or is it possible that I am doing something wrong? I realize that in different executions the system may respond differently. But by always setting the same seed (-s 1), shouldn't the extent of performance degradation be similar for each experiment?