GIPS - Volatility (standard deviation) disclose

2010 edition of the GIPS standards requires firms to present, for each annual period, the annualized three-year ex post standard deviation of monthly composite and benchmark returns and, if appropriate, another measure of risk.

Does it mean

2011 includes 2009, 2010, 2011 monthly data

2012 includes 2010, 2011, 2012 monthly data


Is the intention here to smooth the data?

Why includes three years monthly data in each year?