When it comes to raids on their pocketbooks, the American people seem to have a short and strangely selective span of attention.

For example, the public was outraged over the proposed 50 percent pay raise for Congress - so outraged that the lawmakers were cowed into backing off from it.But where are the complaints about a variety of other efforts by Congress to spend more money on itself? Doesn't the public care about them? Or is it simply unaware of such efforts?

Among the spending increases that Congress is talking about lavishing on itself under the new budget for fiscal 1990 are:

- A $53 million increase in the House of Representatives for employee salaries. The plan allows for new hirings, particularly for clerk and doorkeeper.

- Significant new spending for computers and related services for both the House and Senate. The House, according to the Washington Post, has added $16.2 million and the Senate $16 million for office expenses, primarily for computer-related costs.

- A $9 million increase, to a total of $161 million, in Senate staff and office expense accounts.

But the biggest rip-off involves an exorbitant increase in the franking privilege by which representatives and senators may send out virtually unlimited amounts of mail at the taxpayers' expense.

Next year, Congress wants to spend $114 million on such mailings, the largest amount ever and an increase of $53 million. Much of these mailings amount to campaign literature. No wonder the practice always mushrooms during an election year.

Since 1972, the cost of franked mail has increased nearly four-fold. Even when inflation is taken into account, the cost of franked mail from Congress has exceeded the price spiral by 86 percent.

The least the House should do is to adopt the Senate's practice of letting the public know how much each member spends for mailing costs. Better yet, how about imposing a quota on such mailings? Then how about providing an equal number of free mailings to candidates who seek to replace the current members of Congress?

As it is now, the franking privilege amounts to a way of keeping incumbents in Congress and soaking the taxpayers for this "favor." The public ought to be just as concerned about this practice as it was about the exorbitant pay raise for Congress.