“Historically, changes in employment in Ottawa-Gatineau have explained approximately 80 percent of changes in overall ridership.”
Ridership seems to be closely tied to the number of people employed in the National Capital Region. These are quarterly changes; But how much does employment affect ridership year-by-year? I decided to crunch some numbers myself using annual ridership figures (1996-2012) obtained from various sources: OC's website, a data set in a much earlier article on Transit Ottawa, and monthly employment data of Ottawa-Gatineau region from Statistics Canada. The employment data goes only as far back as 1996. To calculate the annual number of employees, an unweighted average was applied for simplicity.
The data suggests a strong positive relation between regional employment and transit ridership in Ottawa:
About 86% of the variation in ridership can be explained by the number of people employed. When the strike years (2008, 2009) are removed, the relationship is close to perfect:
An astounding 97% of the fluctuation in ridership can be explained by regional employment since 1996, considering OC Transpo serves a small area of Gatineau. But the idea of employment, in general, being nearly 100% correlated to transit ridership is quite remarkable. As we can see, there's very little OC Transpo can do to improve transit usage that will have a similar impact as local job growth.
In order to determine the marginal effect of an additional worker would have on the number of OC Transpo trips, we'll use a least squares regression analysis. With all years included (1996-2012) in the regression, the number of service days affected by the 2008-09 labour dispute is added as a variable. Here are the results of this regression:
As expected, the coefficient estimates of employment and strike days are both statistically significant, even with only 17 observations. This model is a tremendous fit for the data as shown by the R-square of 0.956.
The 2008-09 winter strike is an obvious reason for the temporary drop in annual ridership. The estimate suggests an additional day, weekday or weekend, of the strike decreased 2008 or 2009 ridership by 428 835 trips on average when all other factors are held constant. The number is somewhat high because OC Transpo's figure for ridership on an average weekday in 2012 is 400 000, but appears to be rounded down though.
As for employment, an additional worker in Ottawa-Gatineau leads to an increase of 166 trips or 83 round trips on average, if all other factors are held constant. It's equivalent to nearly four months of transit travel on weekdays. If that person were to buy four monthly passes, that's somewhere between $395 and $488, depending on whether it's a regular or express pass, in annual revenue for OC Transpo. In this case, it's hardly much.
But let's say 500 people lost their jobs in one year and remained out of work the next year. If each worker bought four monthly passes on average while employed, OC Transpo would have lost approximately $197,500 in revenue, on average, the following year. Whether there is a large number jobs created or lost, it will make a noticeable difference in OC Transpo's budget.
Employment seems to have a stronger relationship with ridership on an annual basis than on a quarterly basis. During seasonal changes, other short-term factors emerge like school days, weather, gas prices, or a fare hike. None of them are as economically or statistically significant as the number employed, a variable rarely discussed among everyday transit users going to work.