Some firms that  are under or over  levered may  choose to not  change their  debt 
ratios  to  the optimal.  This  may  arise  either  because they  do  not  share  the  objective  of 
maximizing  firm  value  that  underlies  optimal  debt  ratios,  or  because they  feel  that  the 
costs of moving to the optimal outweigh the benefits. Firms that do decide to change their 
financing mixes can change either  gradually or  quickly. Firms are  much more likely to 
change their financing mixes quickly if external pressure is brought to bear on the firm. 
For under levered firms, the pressure takes the form of hostile acquisitions, whereas for 
over levered firms, the threat is default and bankruptcy. Firms that are not under external 
pressure  for  change  have  the  luxury  of  changing  towards  their  optimal  debt  ratios 
gradually. 
Firms  can  change  their  debt  ratios  in  four  ways.  They  can  recapitalize  existing 
investments, using new debt to reduce equity or new equity to retire debt. They can divest 
existing assets, and use the cash to reduce equity or retire debt. They can invest in new 
projects,  and  finance these  investments  disproportionately  with  debt  or  equity.  Finally, 
they  can  increase  or  decrease  the  proportion  of  their  earnings  that  are  returned  to 
stockholders,  in  the  form  of  dividends  or  stock  buybacks.  To  decide  between  these 
alternatives, firms have to consider how quickly they need to change their debt ratios, the 
quality of the new investments they have and the marketability of existing investments. 
In  the  final  section,  we examine  how  firms  choose  between  financing  vehicles. 
Matching cash flows  on  financing  to  the  cash flows  on  assets  reduces  default  risk  and 
increases the debt capacity of firms. Applying this principle, long-term assets should be 
financed with long term debt, assets with cash flows that move with inflation should be 
financed with floating rate debt, assets with cash flows in a foreign currency should be 
financed with debt in the same currency, and assets with growing cash flows should be 
financed  with  convertible  debt.  This  matching  can  be  done intuitively,  by  looking  at a 
typical project, or can be based upon  historical data. Changes in  operating  income  and  
value  can  be  regressed  against  changes  in  macroeconomic  variables  to  measure  the 
sensitivity  of  the  firm  to  these  variable.  This  can  then  be  used  to  design  the  optimal 
financing vehicle for the firm. Once we identified the right financing vehicle, we have to 
make sure that we preserve the tax advantages of debt, and keep equity research analysts 
and ratings agencies happy.