Tracking a 401K investment

[Joseph Hesse]

Hi,

I have a 401K account from my previous employer from which I receive 
monthly statements indicating whether the amount goes up or down. I am 
thinking of tracking it in the following way

Create Asset:401K and Income:401K

I start Asset:401K with the current value from Equity:Opening Balance. 
If it increases in value, according to my monthly statement, I treat it 
as positive income in Income:401K.  if it decreases in value, I still 
use Income:401K but treat it as negative income.

Is this scheme just a matter of my personal preference or should I do 
something else, like having decreases in value going to Expenses:401K?

Thank you,
Joe