The rating agency, Standard and Poor, reduced its credit rating on 15 big banking companies which were located mostly in Europe and US on Tuesday. The companies which had their ratings reduced by one notch included JP Morgan Chase, Bank of America, Citigroup, Wells Fargo, Goldman Sachs Group, Morgan Stanley, Barclays, HSBC Holdings and UBS. A notch is one third of a letter rating.

S&P also left the ratings of 20 banks untouched and raised the ratings of two in announcing results from its new rating criteria to 37 of the world’s biggest banking companies. The agency also updated ratings for dozens of bank subsidiaries of the companies. S&P had begun warning the markets of a possible reduction in the ratings more than a year ago. The announcement comes at a time when the markets for bank debts are fragile. S&P authorities had said earlier this month they would gradually roll out the updated ratings for more than 750 banking companies worldwide, starting with an announcement of the biggest banks. The remaining announcements of the other banks are due in coming weeks.

The outcome of the revised ratings of the biggest banks was worse than S&P had forecasted for all the banks. S&P officials said earlier this month they expected about 20% of all banks would see their ratings drop, while 20% would have their ratings increased and 60% of the banks under consideration would have their ratings unchanged. In response to growing pressure on their ratings, some banks have updated their contingency plans for a downgrade. They have also refreshed the potential impacts they may suffer through rating downgrades built into obligations under existing derivative contacts, funding commitments and borrowing arrangements.

The share prices of all the companies who saw their ratings downgraded declined further as the news served as the driving force behind the investors pushing the sell button on these companies. However, investors will keep a close eye on the changes in company’s policies in order to push the buy button again.