--------------------------------------------------
Note added at 13 minutos (2013-07-04 12:50:20 GMT)
--------------------------------------------------

em alternativa, fixed rates

e.g.

Investors are assuming that the economy is growing at an accelerated pace, and therefore jumped on Bernanke's response at a press conference that the Fed could begin lessening the rate of buying in the next few months. The result was a drop in stocks and a sudden significant rise in bond yields.
http://horne.vplp.org/2013/06/the-economy-is-too-weak-to-red...

significant increase in the issuance of pre-fixed rate securities


Explicação:
My suggestion, according to the context.


In times of debt, there is an increase in the issuance of securities by the Government.

brazilian treasury securities - The George Washington University
www.gwu.edu/~ibi/minerva/Spring1998/Tarcisio.../Tarcisio.Go...‎
3.5 Segmented Markets, Increasing Liquidity Premiums and Preferred Habitat *. 3.5.1.1 Segmented ... 4.4 Data of the Secondary Market of Brazil Treasury securities. * ... Usually, in order to manage their debt, Governments issue securities

Uma razão para o aumento em 2007 do peso na emissão de títulos de dívida pública de curto prazo relativamente aos títulos de dívida de longo prazo pode ser a subida [...] ecb.europa.eu

One reason for the 2007 percentage increase in governments' issuance of short-term debt securities relative to long-term debt securities could be the rise in long-term interest rates in the first half of the year.


--------------------------------------------------
Note added at 11 horas (2013-07-05 00:14:02 GMT)
--------------------------------------------------

taxas prefixadas = pre-fixed rates