SN4 ""

No	Pattern	Freq
1	[modal v] have been a [noun]	926
2	[vb mod] have been a [noun]	926
3	would have been a [noun]	228
4	would have been a [noun]	218
5	must have been a [noun]	201
6	must have been a [noun]	201
7	[adv] have been a [noun]	196
8	could have been a [noun]	147
9	could have been a [noun]	147
10	[adv] have been a [noun]	137
11	might have been a [noun]	135
12	might have been a [noun]	135
13	may have been a [noun]	128
14	may have been a [noun]	128
15	should have been a [noun]	78
16	should have been a [noun]	78
17	not have been a [noun]	59
18	[not/n't] have been a [noun]	59
19	well have been a [noun]	31
20	well have been a [noun]	31
21	not have been a [noun]	30
22	n't have been a [noun]	29
23	also have been a [noun]	17
24	also have been a [noun]	17
25	'd have been a [noun]	10
26	will have been a [noun]	9
27	once have been a [noun]	8
28	[pron] have been a [noun]	8
29	once have been a [noun]	8
30	even have been a [noun]	7