After a shaky start this morning, it looks as though the S&P/ASX 200 Index (ASX: XJO) is on track for a volatile end to the trading week. At the time of writing, the ASX 200 has pulled back from positive territory and is currently down 0.01%. But let's talk about what's happening with Commonwealth Bank of Australia (ASX: CBA) shares.

Like the ASX 200, CBA shares had a tough start to this morning's trade. The leading ASX 200 bank stock closed at $162.64 a share yesterday, which also happened to be the new all-time record high that CBA clocked that session too.

This morning, investors initially pulled back a little, with the bank opening at $161.64 a share. However, just before midday, CommBank broke into positive territory and quickly rose up to yet another new record high, this one at $162.96 a share.

At the time of writing, investors have cooled off a little, with CBA shares in the red, nursing a 0.15% loss at $162.40 a share.

CBA shares have continued their astronomical 2024 growth into 2025. At current prices, the bank is now up a healthy 6.04% in 2025 to date and is sitting on a 12-month gain of 42.2%.

Check it out for yourself below:

Why are CBA shares at yet another new record high today?

So why are CBA shares pushing up to another all-time high? Well, that's the $272 billion question.

There have been no news or announcements from CBA recently. The last major development from the bank was the revelation late last month that CBA had agreed to sell its remaining 5.45% stake in the Shanghai-listed Bank of Hangzhou Co.

Commonwealth Bank will offload its Bank of Hangzhou stake to New China Life Insurance Co for approximately $940 million in cash.

Investors reacted positively at the time. However, it's unclear if that sentiment is still at play with the current CBA share price.

Another possible explanation is that a combination of super fund dollars and reluctance to sell CBA shares is resulting in the bank's push higher this week.

At the start of the year, we discussed how, with CBA's sheer heft in the ASX 200 Index at present, the regular inflow of superannuation dollars into index funds has become a difficult-to-stop flywheel behind the bank's valuation.

With institutional fund managers and professional investors increasingly reluctant to sell out of their CBA positions (despite its arguably lofty valuation), there doesn't seem to be much downward pressure on the CBA share price.

Let's see how long until we see another new record for CBA shares.