In the early years of parliamentary government members often resigned their seats. One Dunedin member resigned on five occasions during the course of his parliamentary career (without, apparently, prejudicing his ability to get himself re-elected each time).
But, with the development of political parties, resignations became less common and had virtually disappeared for a century until the adoption of MMP in 1996.
Since then resignations have come back into fashion, especially among list members who are replaced by the next unsuccessful candidate on the party list (or even lower down the list if the party "persuades" the next candidate not to take up the vacant seat).
Resignations by electorate members are not so common since they incur the expense and uncertainty of a byelection.
Nevertheless, such resignations do occur - that of Labour's David Shearer in Mt Albert will be the third in the current Parliament.
New Zealand has a three-year term for Parliament. This is short by international standards. Only the United States House of Representatives, at two years, is shorter among major nations.
It is not unreasonable to expect that persons who are elected to Parliament will serve out the full term of this relatively short period. That is, after all, the basis on which they offered themselves for election in the first place.
Yet, increasingly, membership of Parliament for a maximum of three years is seen as being at the convenience of each member perhaps more accurately at that of the member's party, rather than as an obligation undertaken when elected.
Thus there has been a noticeable tendency for list members who are intending to step down at the next election to resign in the final year of the term (either voluntarily or at the party's prompting) so as to make way for a candidate who is expected to have an ongoing interest in a parliamentary career.
In this way, for many members, the already short parliamentary term becomes an even shorter one. For every member a parliamentary career is converted into something that one has the ability to leave costlessly in political terms at any time, rather than being a commitment to public service for the life of a parliament.
In my view this is deleterious to the institution of Parliament and to the sense of obligation that members should feel to it.
"New blood" is infused into Parliament at the not infrequent intervals that a general election provides.
It does not require members to retire early to provide it. Members in the final year of a Parliament can and should be expected to contribute to its work for the full term that they have signed up to regardless of their intentions to stand or not at the next election.
Consequently, there should be stronger disincentives both to members and to parties to prevent the early jumping of ship that has become endemic.
In the case of list members, the remedy is quite simple: any vacancy occasioned by resignation should not be filled.
List members, whatever they may pretend to the contrary, are not elected to represent individual constituencies of a geographical or other nature.
Our electoral system allows the voter to make no such distinctions when casting a party vote.
So there can be no question of a denial of representation in leaving such seats vacant.
But that is not the point. Not filling such a vacancy would largely eliminate list resignations as they are almost always promoted by the parties themselves.
They would cease to occur if this meant that a party's votes in Parliament would be permanently reduced.
Electorate members, on the other hand, do represent constituents and it is unacceptable not to full such vacancies.
The present law allowing vacancies arising within six months of a general election to be left unfilled is inherently undemocratic and should not be extended.
But resignations occurring further out from this period need to be discouraged.
Consequently, as a condition of being declared elected, electorate members should be required to enter into a bond to serve through the full term of the parliament.
The amount of the bond would not cover the full cost of a byelection (indeed, that would not be its intention) but it should be sufficiently high to provide a financial disincentive to resignation for the member and for the party backing the member.
In the case of both list and electorate members, resignation without these consequences would be permitted on health grounds proved to the satisfaction of the Speaker or the Electoral Commission.
This would be rare. I can think of only one member whose resignation was at least partially triggered by concern for his health.
Resignations from a parliament with as short a term as ours has dramatically increased since 1996.
It has become a real problem for the Parliament and, although not all members would acknowledge it, for the effectiveness of members themselves.
Membership of Parliament ought not to be a mere convenience for political parties, nor should it be a status that can be discarded lightly. It is time that this undesirable development was addressed.