# How to increase the vertical offset of exponent terms with increasing size of parentheses?

I want to be able to write the following expression:

But have not been able to do so, since all I can get is:

I do not use the fraction of P/E, but rather just the psi. Can you help?

EDIT: After the suggestion of \left (and \right), I have managed to produce the following:

$$\hat{\psi}_{p,t}=n\displaystyle \left(\sum_{j=1}^{n}\big(\psi_{j,t})^{-1}\big)\right)^{-1}$$


But it does not seem as if \big has an effect?

• What is wrong with \left(, \big(, etc.? – user156344 Apr 17 at 10:25
• \big(, \bigg(, \Big(, \Bigg(, etc. You have tons of options. – user156344 Apr 17 at 10:30
• I added your suggestion, but it does not seem as if \big has any effect? Maybe I haven't understood the command properly – Philip Apr 17 at 10:31
• It does have effects, but the brackets are not really bigger, only slightly. Read my comment above. – user156344 Apr 17 at 10:31
• – Steven B. Segletes Apr 17 at 10:36

As far as I can tell, there is no need whatsoever to increase the size of the inner parentheses, if the term they enclose is \psi_{j,t}. For the outer parentheses, choose \biggl( and \right) -- using \left( and \right) would result in parentheses that are too tall, typographically speaking.
\documentclass{article}
$\hat{\psi}_{p,t}=n\biggl( \sum_{j=1}^{n} (\psi_{j,t})^{-1} \biggr)^{\!-1}$