In the example given by Phzon the fields were exactly the same - 180 man SNGs.
I play $4 Rush SNGs and, with on-demand, field sizes are much bigger and this has significantly effected my ROI
In these games a top 10% finish is ITM and my distribution (below) is almost identical - based on 500, 135 Rush, $4 SNGs (and 600 On demand tournaments - average entries 300+)
Finish
Top 10% 13% (14%)
11-20% 13% (14%)
21-30% 12% (12%)
31-40% 14% (13%)
41-50% 14% (14%)
51-60% 14% (14%)
61-70% 12% (13%)
71-80% 5% (4%)
81-90% 1.5% (1%)
91-100% 1.5% (1%)
However, my ROI is completely different - 23% in the 135 field, 7% in the larger fields.
IMHO this is because in the 135 field, doubling up near the bubble or just ITM, almost guarantees a FT finish, whereas if you just creep ITM in the bigger field you need to double 3 or 4 times to get to FT.
Cheers
Jass