For the 17th straight month, the Case-Shiller Index reports that home values are rising across the United States. As compared to June, July’s prices were up by 4 percent.

However, despite the improvement, July’s Case-Shiller Index showed weaker as compared to prior months.

• In June, just 3 cities posted year-to-year reductions in home value. In July, 10 of 20 did.
• In June, just 1 city posted a month-to-month reduction in home value. In July, 7 of 20 did.

As a spokesperson for Case-Shiller said, values “crept forward” in July. But not that it matters — the Case-Shiller Index is a better tool for economists than it is for homeowners in Oak Park. This is for 3 reasons.

First, the Case-Shiller Index is on a 60-day delay but real estate sales are based on prices today. A lot can change in 60 days, and it often does. Therefore, the Case-Shiller Index is a better snapshot of the former market than the current one.

Second, the Case-Shiller Index is geographically-limited. It tracks just 20 cities, ignoring some of the largest metropolitan areas in the country including Houston, Philadelphia, and San Jose. Smaller cities like Tampa are included.

And, lastly, national real estate data remains somewhat useless anyway. All real estate is local, rendering citywide statistics too broad to have any real meaning to an individual. To find out what’s happening on a neighborhood-by-neighborhood level, you can’t look to a national survey — you have to look to a local real estate agent instead.

According to the Standard & Poors Case-Shiller Index, home values rose 5 percent in June versus the month prior, and 4 percent from a year earlier.  It’s the 16th consecutive month in which Case-Shiller reported an increase in home values and the third straight month of outstanding results.

That said, homeowners and home buyers in Chicago would do well to temper Case-Shiller enthusiasm. The June figures are issued on 60-day delay and, over the last 60 days, housing data has been lackluster at best.

• Existing Home Sales are down 27 percent
• New Home Sales are down 12 percent
• Homebuilder confidence is down

Stories like these highlight a key weakness of the Case-Shiller Index — it’s out of date as soon as it’s published. Because of this, the Case-Shiller Index relevance to everyday Americans is muted. People don’t buy homes in the “60 days ago” real estate market, after all.

June is ancient real estate history to buyers and sellers in Wicker Park.

However, the Case-Shiller Index does have its place. As the most widely-followed, private-sector housing tracker, the index is used to help make policy decisions and to shape Wall Street’s expectations of the economy. This means that a strong Case-Shiller reading can cause mortgage rates to rise, and a weak Case-Shiller reading can cause rates to fall.

Tuesday, mortgage rates fell.