Table 1: Length, pattern and occurrence of all null-groups in our sample. By definition, events always start and end with nulls. N denotes a null, P a pulse. Symmetric patterns are treated as one: NPNN for example is a combination of NPNN and NNPN. Within a group, observing a pulse is 1.2 times more likely than observing a null.

Event	Pulse-null	# of			Total
length	combinations	events	# N	# P
1	N	361
2	NN	76
3	NNN	27	27	0	27
	NPN	52	0	52	52
4	NNNN	16	32	0	32
	NPPN	13	0	26	26
	NPNN	19	19	19	38
5	NNNNN	1	3	0	3
	NPPPN	2	0	6	6
	NPPNN	1	1	2	3
	NPNPN	1	1	2	3
	NPNNN	4	8	4	12
6	NNNNNN	1	4	0	4
	NPPPNN	2	2	6	8
	NPPNPN	3	3	9	12
	NPNPNN	2	4	4	8
	NPNNNN	1	3	1	4
	Total:		107	131	238
	Fraction		.45	.55	1