Agnes Crane – Agnes T. Crane is a Reuters columnist. The views expressed are her own –

Reasons people give to explain the quick switch-back movements in stocks and other risky assets are becoming, well, just bizarre.

On Monday, it was the World Bank’s dire outlook for the global economy — no matter that the organization’s president already said output was likely to decline by close to three percent earlier this month.

On Tuesday, it was Moody’s Investors Service reaffirming the Aaa rating of the United States that gave stocks a brief lift, even though few expected any rating agency to make a move on its credit standing any time soon.

Investors should take these kinds of explanation and moves with a grain of salt, especially during the summer months when trading volumes are light and conviction easily undermined.