Some definite light has been shed to make clearer the ongoing debate about the cost of the MLP's proposals to stimulate the economy, should Labour win the coming general election.

The main proposals cannot be costed with any reasonable degree of certainty. In particular, the cost of halving the water and electricity surcharge can only be known at the time the deed is done, and will keep changing with the price of crude oil. The assumed figures being bandied about now are already way out, given the way the international oil price has been accelerating.

The cost of subsidising first-time home buyers - once that is what this particular proposal boils down to - is not difficult to arrive at. The figure I gave in this column last week can be estimated with near certainty. With the one per cent interest subsidy restricted to first-time borrowers, say 2,000 annually, it would amount to Lm1 million in the first year, rising thereafter with new borrowers, if the base rate stays above 4.5 per cent. A far cry from the Government's Lm60 million claim.

The cost of adding back public holidays which fall on a weekend to the annual leave entitlement is also clear enough. It depends on the number of restituted days in a particular year. The most controversial Labour proposal is to exempt overtime earnings from income tax. The Government says it would cost an estimated Lm12 million per annum, plus another Lm18 million in presumed abuse. Such presumptions are subjective. Take, then, the Government's estimate as Lm12 million. The Opposition counters that with an estimate of Lm2 million.

Both sides, it is now pretty clear, are wrong, going by the light shed on the issue by the National Statistics Office (NSO). In Sunday's column I asked whether the NSO could give an official estimate of overtime earnings.

The NSO did not give such an estimate, but provided the basis on which a serious one could carried out. In a letter featured in the correspondence columns today the NSO says that an internal exercise, corroborated by two mutually independent sources (the Labour Cost Survey and national accounts estimates), puts the component of overtime earnings at between Lm42 million and Lm47 million annually for the period 2004-2006.

Use that range as a base, with Lm47 million for 2006, and then peer into 2008, when the measure would become operative, should Labour win the election. Next year there will be two relevant developments. One, an increase in nominal wages and salaries. At a minimum they will rise by the equivalent of the Lm1.50 per week cost-of-living increase. Furthermore, the income tax adjustments proposed in the Budget will take effect. Thereby overtime income will be taxed at 15 per cent, according to the Treasury's working as the basis for the lower tax-band adjustment.

Taking these figures together allows the strong assumption that in 2008 total income from overtime will be around Lm50 million. Taxed at 15 per cent, that would yield Lm7.5 million. The direct cost of Labour's overtime proposal, therefore, would be roughly halfway between what the Government and the Opposition are predicting.

Can't they, at least, use an objective approach to allow their estimates to converge, rather than parroting Lm115 million on the Government side, and Lm15 million on Labour's?

Clearly both figures are wrong, with the Government's being the more awry, both because of mistaken assumptions (such as a Lm5 million monetary cost to the Government to restore public holidays and feasts to its employees, Lm60 million for interest subsidies, and its blowing up of the overtime foregone income). Economists who venture into the debate could give a helping hand with objective estimates of their own, rather than bland, unsupported statements of the good or bad implications.

At the end of the day, where is the beef? Certainly not in buying votes with (Opposition) promises or (Government) scaremongering. It should lie in strengthening the economy by making it more competitive. Competitiveness, to extent that we can influence it, depends on new investment incorporating technological innovation, on labour costs and productivity - and to what extent competitor countries are putting this package together, compared with us.

Competitiveness and growth will not come through endless debates on assumed figures. It is understandable that politicians want to stimulate consumption. That is what this Government aimed for with its tax cuts in 2007 and those proposed for 2008, plus the increases in social benefits irrespective of means. That is what the Opposition is aiming to do with its package of proposals.

But it is export-oriented investment which brings sustainable economic growth. What the politicians should be debating, without fudge, is how they propose to attract more direct investment. That is what economic reality is all about. That is what the standard of living and real assistance to the most needy depend on. Hot air and continued flogging of wrong figures are not the solution.