I've never understood this argument. When performing scientific studies, there is a sample size of n = x hundred/thousand, and we then generalise the result across the entire population. Having 48% of the population participate in this "study" is likely to be very indicative of the likely voting choice for the remainder of the population, right? You really think that the proportion of votes for each party for those people that haven't voted would be any significant difference from those that did?