Novel measures for vowel reduction are presented, for examining vowel space as a whole, and for quantifying reduction of individual vowels. These were used to evaluate the degree of vowel reduction in continuous speech, manifested in the F1-F2 plane. The measures were applied to a set of 1500 tokens, extracted from a database of spontaneous Hebrew speech. Using a similarity measure, we found that vowels were reduced by a factor of 2.09 for men and by 2.93 for women. The reduced vowel space for men was more distorted than for women. Error measure estimations were larger for men in comparison to women (0.0714 versus 0.0525, respectively). While vowel reduction in women exhibited a relatively symmetric pattern across vowels, it showed a skewed pattern in men. This was attributed to a more pronounced reduction in the back vowels /o/ and /u/.