SINGAPORE - Since January, oil prices appeared to be the prime driver of stock market sentiment.
Indeed, if you super-impose a chart of oil prices in the past few months over that of a major stock index such as Wall Street's S&P 500 or the benchmark Straits Times Index here, you would have found quite a good fit between them.
However, this correlation has broken recently.
Oil prices have climbed back past the US$50 level for the first time since November as it almost doubled in prices after hitting 12-year lows in January.
But its rally has not propelled a similar run-up in regional equity markets.
The one feature worth highlighting about the recent performance of regional markets is the lack of interest displayed by investors. The daily stock turnover in Singapore this week, for instance, is well below the $1 billion level which had been the daily average turnover for the past five months.
Now, that conspicuous lack of appetite for regional stocks may be a tad surprising considering that the rebound in oil prices should have eased concerns in a number of areas.
These include lessening the likelihood of further cutbacks in oil-majors' capital expenditures in order to conserve their cash resources to continue to pay out their mouth-watering dividends.
That should in turn, be good news for stocks which have been hurt by falling demand for rigs rented out to oil majors, and offshore supply vessels which provide a wide range of services for the offshore oil exploration sector.
Any uptick in business for companies in the beleaguered offshore and marine stocks would also alleviate the pressure which banks must be facing on the loans which have been extended to them.
The bounce in crude prices will also ease fears that oil-producing countries may be forced to offload assets from their investment portfolios in order to raise funds.
As such, a pick-up in oil prices should be fuelling riskier bets in regional equities. But this has not turned out to be the case.
Instead, a host of concerns that spooked investors early this year are continuing to stalk the market, lending credence to the "sell in May and go away" theory.
In particular, there are two key events occurring next month which could explain why traders are content to sit it out on the sidelines.
One event is the referendum which the United Kingdom is holding on June 23 to decide whether to leave the European Union. The big worry is that any decision to exit may plunge Europe into a major political and financial crisis.
And until the poll is over, traders may prefer to adopt a "safe rather than be sorry" approach and stay on the sidelines.
The other event is the United States central bank's interest rate fixing meeting one week before the UK referendum.
The minutes from the Fed's April meeting suggested that an increase in short-term interest rates is a real possibility this summer if the US economy continues to improve.
If an US interest rate hike takes place either in June or July, followed by another hike in December after the US presidential elections, it would have been in keeping with the US central bank's agenda set out in March to limit the number of rate increases it expected for this year to just two quarter-point moves.
But any rate hikes will be bad news for stock traders who are used to the fat cushion of cheap money furnished by the Fed to underpin stock prices since the global financial crisis eight years ago.
One outcome of the shortening odds on a Fed rate hike is the strengthening of the US dollar against other currencies such as the Japanese yen and the euro.
That, in turn, revives a no-brainer strategy on how to beat the market and that is simply to track how the US dollar is doing.
For much of the past eight years since the global financial crisis, stock prices would shoot up whenever the greenback wobbles, and turns weak when it strengthens. Expect this relationship to continue to hold true as the Fed tightens the screws on interest rates.