The person you bought your home from lived in it as of January 1, 2006, therefore they qualified for the home owners exemption (HOE) for their 2006 taxes, paid in 2007. You lived in your home, that is it was your primary residence as of January 1, 2007 therefore you qualified for the HOE on your 2007 taxes, paid in 2008.
The reason the homeowners exemption is different is because in 2005 the IL legistrature pass a 7% Rule, which basically said, in reference to the HOE, if a property sells the after 2005 the homeower will get the minimum tax break. (The maximum being 20,000 off the assessed value, the minimum being 5,000 off the assesed value which in 2008 equalled $460)

Since you bought your condo, Oak Park has been reassessed. There was a reassessment in 2005 and 2008. If your assessed value remained the same from 2004 to 2007 I can only guess you are in a building that either experiences very few sales, or there some type of freeze on the assessed value. Perhaps you bought from a senior citizen.

I agree with Alex, you should always appeal your taxes. The Oak Park Township Assessors Office is a great resource for helping understand your property taxes. You can reach them at 708.383.8005. Ask for Ali or Shelley.

Dorothy Reid
Baird & Warner
805 W Lake St
Oak Park, IL 60301
708.702.4768

This has happened to a lot of condo owners in Oak Park, myself included. Your taxes are assessed every three years by Cook County. If your building was recently (since 2004) converted into condo's then this is most likely the problem. Until 2007-2008 your building may still have been precieved as an apartment building in Cook County's eyes. When the developer came in and rehabed the building and converted the property into condo's the property's taxes were very low. Now 3 years later in 2007 Cook Country reassessed the building seeing that major improvements were made increasing the value of the property. This caused the recent jump in your taxes.

For example my 1 bedroom condo on Harrison St. taxes went from:

2004- Building was converted from apartments to condos - $800/year
2005 - $850/year
2006 - $900/year
2007 - Cook Country reassessment year - $4,200/year

You are not alone in this situation. It is rather brutal and significantly increases your monthly payment for taxes. Keep making sure that your homeowners tax exemption is filed and always contest your taxes every year. It is one of the simplest things you can do, you can even do it online via the Cook County assessor's website.

Please let me know if this answers your question or need anything else!