Table 1: Number of 1-h data sets for each time series, and the monthly spot number at the time of each series (SIDC, 1996-2006).

Time series	# Hourly sets	Spot number
August 1996	35	14.4
January 1997	40	5.7
March 1997	14	8.7
April 1998	29	53.4
October 1999	33	116.7
October 2000	38	99.4
February 2001	31	80.6
December 2002	25	80.8
May 2003	45	54.6
May 2004	53	39.3
September 2005	21	21.9
July 2006	87	12.2