year	stat	spm_	so2_	no2_
1987	"mean"	279.28	21.02	29.26
1987	"N"	20	17	18
1988	"mean"	243.62	18.73	23.23
1988	"N"	25	25	25
1989	"mean"	245.73	18.2	26.18
1989	"N"	31	31	31
1990	"mean"	249.14	19.91	24.86
1990	"N"	44	43	43
1991	"mean"	256.17	20.3	28.78
1991	"N"	47	46	45
1992	"mean"	223.48	20.85	28.5
1992	"N"	58	57	57
1993	"mean"	257.16	22.49	27.85
1993	"N"	66	64	63
1994	"mean"	249.33	22.24	28.47
1994	"N"	58	65	65
1995	"mean"	215.96	22.15	23.31
1995	"N"	42	41	43
1996	"mean"	244.92	21.93	25.9
1996	"N"	70	68	68
1997	"mean"	213.57	23.59	30.03
1997	"N"	76	72	72
1998	"mean"	229.75	21.74	27.69
1998	"N"	68	66	66
1999	"mean"	221.5	22.05	29.08
1999	"N"	77	75	75
2000	"mean"	193.5	16.71	27.76
2000	"N"	68	71	71
2001	"mean"	222.95	14.74	27.32
2001	"N"	57	69	70
2002	"mean"	189.42	12.97	26.71
2002	"N"	67	77	77
2003	"mean"	230.25	11.94	26.46
2003	"N"	76	76	76
2004	"mean"	221.42	11.64	26.14
2004	"N"	82	85	85
2005	"mean"	210.63	12.71	26.71
2005	"N"	97	86	93
2006	"mean"	202.91	12	24.97
2006	"N"	116	104	115
2007	"mean"	206.66	12.41	24.91
2007	"N"	125	106	124
