Indeed, when the risk-free rate - that of ten-year US Treasury bonds - hovers around 5%, investors naturally demand a risk premium for dividend-paying stocks, which varies according to the growth potential of the underlying businesses.

For groups like AT&T or Verizon, deprived of non-inflationary growth, it is therefore natural that valuations automatically adjust downwards to ensure yields in the 7-8% range, i.e. the 5% risk-free rate plus a risk premium of between 2% and 3%.

Added to this is the hotly debated scandal surrounding the lead cables laid by these operators over the last century, and the risk of legal action for breaches of environmental regulations: the case could cost the two companies dearly.

These developments have sent AT&T's share price back to its all-time lows - levels it hasn't reached in twenty years.

All we can see here is a very healthy evolution and, rather than a correction, a return to rational valuation levels in view of the interest rate environment. As already mentioned, telco operators are not growing, while their hyper-capital-intensive activities consume ever-increasing proportions of their operating cash flow.

In this respect, the best we can expect from them is a stable dividend payout over time. This does not appear to be under threat at AT&T. On the other hand, rising interest rates could severely increase the cost of debt.

Against this backdrop, and despite encouraging quarterly results, it is hard to see AT&T being in a position to increase its dividend payout if it is to maintain the coverage ratios required by its creditors.