We can't do it anymore!
When Fiona was about 16 months old, we counted up the words we knew she could say (and understand). We had a list of about 75 words. There might have been 5 or 10 more that we missed, but 75 was a pretty good estimate. That was the last time we counted.
When Nora turned 16 months old, we counted up the words we knew she could say. We'd kept closer track this time, thanks to this blog. We had a list of about 75 or 80 words. And once again, that was the last time we counted, or even made any attempt to keep track.
They both hit about the same milestone at the same age, and then ... they both really hit their stride. They both started gaining new words at breakneck speed. The rate of their language acquisition experienced an explosion that we simply couldn't keep up with, even with the added tool of the blog - we try to post something every day, but (as I'm sure you've noticed), we don't always succeed. If we miss two days and then post at the end of the third day, we've heard so many new words that we can't keep them straight. Of course, if we weren't quite so sleep-deprived, we might have been able to come up with an even better system to keep track, but hey, it's too late now. It's just a guess, but Nora may have doubled her list by now - less than a month after we made the comparison with Fiona's list.
According to a popular baby web site, this vocabulary spurt comes, on average, around 18 months. So they're just a couple of months early. That's reassuring, actually - we're not trying for geniuses or anything. But we certainly have verbal kids.