Your partner and the opposition have shown hands of less than opening values and may well continue to pass, and Partner is entitled to pass any natural bid made. So a stronger fourth seat hand may not have an opportunity to bid again.

Additionally, if fourth seat opens at the one level with a stronger hand and the opposition preempts at the two level or higher, fourth seat's partner may not be able to bid if holding two or three quick tricks in the outside suits. A 1NT response is no longer available.

Therefore, a bid made made by fourth seat should be intended for a successful contract and not be pre-emptive. A number of bridge authors have looked at such situations.

If, after three passes, fourth seat has S 74; H KQT9863; D AQ5; C 2, the best opening bid is 3H, inviting Partner to bid to game if holding two or three quick tricks. It is not a pre-emptive bid. 

If this hand had been held in seats one, two or three, then the best bid would have been 1H.  A 1H bid in fourth seat would have shown a basic opening hand with an expectation to play in a part-score contract.  

CONGRATULATIONS to Bob and Lyn Dillon, Phil Cummings, Dick Ellis, Elaine Walker, Lorraine Johnson, Chris Rosevear, Karin le Roux, Trish Burke, Marie Dennis, Glen Thwaites, Anne Hunter, Joy and John Adams, and Lee Harris who all won both the outright and the handicap competitions in recent events.