The S&P/ASX 200 Index (ASX: XJO) is advancing on Wednesday, even as new data indicates a deceleration in Australia's economic momentum.

Currently, the ASX 200 has risen 0.59% to 8,775 points.

This upward movement brings the benchmark index near its daily peak of 8,779.8 points and close to its recent highs. However, the market's performance beneath the surface remains uneven, with a select group of major stocks contributing the bulk of the gains.

So, what is motivating investors to continue purchasing?

Market Participants Overlook Tepid GDP Figures

The most recent national accounts revealed that Australia's economy expanded by 0.3% during the March quarter.

Annual GDP growth decelerated to 2.5%, coming in slightly below economists' forecasts.

Growth was constrained by weak household and government spending, reduced mining output, and a negative contribution from net trade, according to the ABS.

Business investment, particularly in data center machinery and equipment, stood out as a primary positive driver.

The modest growth figure has failed to push the ASX 200 lower. Instead, investors seem to be interpreting it as further evidence that interest rates may not need to increase from current levels.

Markets displayed minimal reaction to the data, with swap markets indicating only a slight probability of another rate hike next month.

Resource Sector Provides the Momentum

The session's strength is being driven by the S&P/ASX 200 Resources Index (ASX: XJR), rather than a widespread market rally.

BHP Group Ltd (ASX: BHP) shares are up more than 2% to $64.91, while Rio Tinto Ltd (ASX: RIO) shares are also trading more than 2% higher at $195.84.

Sandfire Resources Ltd (ASX: SFR) shares have surged as much as 3.2% to $20.64.

This buying activity coincides with copper futures trading near record highs following a robust performance earlier in the week. This has provided investors with an additional incentive to re-enter major mining stocks, even as the domestic economy shows signs of softening.

Gold miners are also performing strongly. Northern Star Resources Ltd (ASX: NST) shares are up approximately 6.2% to $22.34, building on yesterday's 13.6% rally.

Uranium companies are contributing to the gains, with Paladin Energy Ltd (ASX: PDN) shares advancing 10.2% to $11.69, Deep Yellow Ltd (ASX: DYL) shares lifting 7.1% to $1.62, and Boss Energy Ltd (ASX: BOE) shares climbing 7.5% to $1.38.

A Broad-Based Rally Is Absent

A crucial observation is that today's gains are not being distributed uniformly across the market.

Earlier in the session, only 77 of the ASX 200's 200 constituent stocks were trading positively. This indicates that while the index is rising, the buying interest remains concentrated within a narrower group of large resource and energy companies.

Commonwealth Bank of Australia (ASX: CBA) shares are up 0.4% to $166.36, providing some support to the benchmark. However, several other major stocks are moving in the opposite direction.

CSL Ltd (ASX: CSL) shares are down around 1.2% to $91.46, while the S&P/ASX 200 Information Technology Index (ASX: XIJ) is also facing downward pressure.

Xero Ltd (ASX: XRO) shares have declined 3.8% to $83.70, and WiseTech Global Ltd (ASX: WTC) shares are 2.5% lower at $41.15.