need to determine the monthly returns for each category before calculating the time-series average returns and standard deviations of the size premiums across the six regions/countries. calculate the monthly returns across the six regions?                                                                                  

Year	Month	Market Risk Premium (Rm - Rf)	Size Premium Across Regions (SMB, Small-Minus-Big)
Global Market	Developed Market	Emerging Market	European Market	Japanese Market	Asia-Pacific Market Excluding Japan	North American Market
1993	1	0.31	1.59	-1.57	3.28	-1.67	0.31	2.01
1993	2	1.89	-1.27	3.08	-0.79	2.09	-1.47	-3.61
1993	3	6.67	0.35	1.55	1.43	0.26	3.76	0.6
1993	4	4.3	0.59	4.12	3.46	1.07	3.73	-0.37
1993	5	3.12	4.35	3.34	0.29	12.26	2.72	2.04
1993	6	-2.11	-0.9	-2.59	-1.58	-2.64	2.44	0.46
1993	7	2.25	-1.54	0.71	-1.1	-4.79	1.11	0.9
1993	8	4.37	0.86	1.24	0.53	-0.51	-1.38	0.48