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"Haven't we seen a chart showing that the gross rent multiplier in irvine has NEVER been 160, and was hovering around 200 before the 'boom'?"
Not a chart based on real market rents. The data you were referring to was based on the rental equivalent component of the CPI -- a made up number. Market rents will always be reflective on income because rents are paid out of current income. Look at the income data from 1997, and look at the median sales price, and what do you see?
Irvine Median Income Irvine Median Rent GRM
2006 $ 83,891 $722,928 $ 2,500 289.17
2005 $ 82,827 $635,675 $ 2,468 257.54
2004 $ 80,520 $609,397 $ 2,400 253.96
2003 $ 75,141 $461,888 $ 2,239 206.27
2002 $ 72,289 $379,852 $ 2,154 176.33
2001 $ 71,821 $334,741 $ 2,140 156.40
2000 $ 72,057 $308,089 $ 2,147 143.47
1999 $ 68,170 $278,148 $ 2,032 136.92
1998 $ 63,959 $263,172 $ 1,906 138.07
1997 $ 62,022 $245,437 $ 1,848 132.79
If you assume the rent on a median home in Irvine was $2,500 a month in 2006, you can take the same percentage of income and extrapolate backward to obtain the median rent back to 1997. We know what the median home price was. Once you have a rental rate and the median home price, the GRM is an easy calculation.
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Wouldn't it be more accurate to compare rents to average monthly payment? Last time I checked landlords primarily base their rents on their monthly payments, and renters decide whether it is better to rent or own based on monthly mortgage payments as well.
Would the GRM be the same if you did that?