03/12/2013. The average number of contributors to the Spanish Social Security System in November 2013 stood at 16,293,543. Although this figure is down 66,829 (-0.41%) on the previous month, it reflects a better result than in 2012 (-205,678) and 2011 (-111,782). In seasonally-adjusted terms, net employment remained practically unchanged with a fall of only 2,828 in the average number of people contributing to the system in the month.