Outage capacity is one of the widely accepted metrics to predict the maximum reliable information rate over fading channel with channel side information (CSI) at the receiver only. This metric is calculated with the assumption that since CSI is not available at the transmitter side, transmission strategies such as rate adjustment cannot be employed to match channel varying to improve the system spectral efficiency. But it is possible to adjust transmission rate at the receiver side instead of adjusting at the transmitter side. In this case, is the widely accepted concept on outage capacity still true? To answer this question, we evaluate spectrum efficiency of two different systems that use rateless codes for several modulation schemes over Rayleigh flat fading channel by theoretical analysis and simulation in the paper. It is shown that outage capacity cannot be well used to predict maximum reliable information rate for fading channels in middle regime of signal to noise ratio.