When your annuity is linked to the returns on investments of an insurance company that earns profit with equity release, it is called the with profit annuity for you.  However the income that is payable can both go up and come down depending on the fluctuation of market conditions. The advantage however is that such annuity provides smoothed returns on your investments.  

This is a novel term.  This means that your income on your investments will not go down as much as you desire during the lean season.  The drawback is that in salad years you may not get back all the investment returns.  Still the returns are not as volatile as in case of many other plans. 

Broadly speaking, your investment could generate two types of income.  The first is the minimum starting income.  They are normally set at low levels.  But unless and until conditions are very bad you will be assured of at least this much of income like it happens in the mortgage protection. 

Insurance companies will usually announce bonus every year.  They may be reversionary that means they are traditionally paid every year or special. Among various factors determining the amount of bonus, the stock market fluctuation is the most important one. 

For profit annuities you will be selecting some anticipated rate of bonus.  The rates will vary with each provider but the normal range remains 0% to 5%.  The problem is that once the same is selected by you there is no scope to change it.  However the extra amount earned in terms of bonus could be real beneficial for cases like critical illness insurance.