Year	April	September	April trend	September trend
1979	32.295	16.911	32.295	16.911
1980	31.807	16.316	31.99	16.576
1981	30.034	12.808	31.686	16.242
1982	28.302	13.508	31.381	15.907
1983	30.17	15.2	31.077	15.573
1984	29.816	14.635	30.772	15.238
1985	30.517	14.583	30.468	14.903
1986	30.456	16.076	30.163	14.569
1987	31.502	15.353	29.858	14.234
1988	30.213	14.987	29.554	13.899
1989	29.621	14.77	29.249	13.565
1990	28.905	13.815	28.945	13.23
1991	30.005	13.593	28.64	12.896
1992	29.259	15.078	28.336	12.561
1993	29.575	12.441	28.031	12.226
1994	29.312	13.855	27.726	11.892
1995	27.311	11.236	27.422	11.557
1996	27.255	13.949	27.117	11.222
1997	28.741	13.228	26.813	10.888
1998	28.823	11.626	26.508	10.553
1999	27.924	11.045	26.204	10.219
2000	26.689	11.084	25.899	9.884
2001	26.87	12.275	25.595	9.549
2002	26.822	10.846	25.29	9.215
2003	26.273	10.284	24.985	8.88
2004	25.308	10.037	24.681	8.545
2005	25.354	9.283	24.376	8.211
2006	24.337	9.113	24.072	7.876
2007	23.094	6.526	23.767	7.542
2008	24.122	7.25	23.463	7.207
2009	23.88	6.925	23.158	6.872
2010	22.223	4.742	22.853	6.538
2011	21.139	4.48	22.549	6.203
2012	21.714	3.787	22.244	5.868
2013	21.865	5.479	21.94	5.534
2014	21.913	6.972	21.635	5.199
2015	23.027	5.852	21.331	4.865
2016	21.026	4.53	21.026	4.53