--- title: Year Over Year (YoY) — definition for seasonal businesses | Siite description: "Year-over-year comparison explained: why month-over-month misleads in a seasonal business, and which numbers are worth comparing across years." url: "https://siite.co/dictionary/year-over-year" type: static generatedAt: "2026-10-22T08:21:10.864Z" --- Metrics & Analytics # Year Over Year Comparing a period to the same period last year rather than to the previous month — the only fair comparison in a business with seasons. Also goes by YoY, Year on year [![Siite](/images/layout/logo.svg)Written by Siite](/about/)Updated September 8, 2026 ## Entry contents [All Terms A to Z←Browse the full dictionary](/dictionary/) A year-over-year comparison puts a period next to the same period a year earlier: this July against last July, this quarter against the same quarter last year. In a business with seasons, it is the only comparison that answers the question people think month-over-month is answering. > **Briefly explained** > > - This period against the same period last year. > - It removes the season from the comparison. > - Month-over-month in a seasonal business mostly reports the weather. > - It needs a year of history before it works at all. ## Why does month-over-month mislead? Because the two months were different markets. Demand in most local businesses moves with the calendar: weather, holidays, school terms, storm seasons. A report showing leads down forty percent against last month, in the month where that always happens, describes the calendar and nothing else. Worse, it invites a decision. Budgets get cut in a slow month that was always going to be slow, and the following season starts from behind. ## What is worth comparing across years? The numbers that describe the business, not the website. - Booked jobs, by service - Revenue by department - Cost per booked job. See [cost per lead](/dictionary/cost-per-lead/) for why the lead number alone is not enough. - Review count and the pace they arrive at - Organic and paid leads separately, because they move for different reasons ## How do you use it well? - Compare like periods: same month, same quarter, with weekdays or dates chosen deliberately - Note the one-off events that make a year incomparable, and keep the note - Expect noise if you are small. One unusually large job can distort a quarter and prove nothing - Judge changes you make now against this period next year That last point is unpopular and accurate. Most marketing decisions cannot be honestly evaluated inside a season. ## What do the terms mean? - **YoY:** The abbreviation, used on most dashboards. - **MoM:** Month over month. Useful in a steady business, misleading in a seasonal one. - **Like-for-like:** Comparing periods that are genuinely comparable. - **Seasonality:** The predictable pattern in demand across a year. - **Baseline:** The stable number you compare against when you have no history yet. Owner questions ## What owners ask us about Year Over Year ### Why not compare to last month? +Because in a seasonal business last month was a different market. October against September tells you the weather changed, not whether your marketing worked. ### What if last year's data is unreliable? +Use it and note the caveat, or compare against the same period two years back. An imperfect seasonal comparison still beats a clean but meaningless one. ### Does it work for a new business? +Not until you have a year of history. Until then, compare against a stable baseline such as cost per booked job rather than against traffic totals. ### How do I handle a one-off event? +Note it on the report rather than editing it out. A storm, a freeze or one large job can distort a quarter, and the note is what stops somebody drawing a conclusion from it next year. ### Should I compare the same dates or the same weekdays? +Same weekdays for anything driven by business days, same dates for anything driven by weather or holidays. Pick one, write it down, and keep using it.Put this to work ## Guides that use this Step-by-step playbooks from the team, written for owners doing the work themselves. No sign-up and no email required. [### Texas HVAC summer ad-spend curve: why doubling July loses money Most Austin HVAC operators double their Google Ads budget in July. CPCs rise faster than demand and ROAS collapses. Here's the curve we run instead. Read the guide→](/articles/texas-hvac-summer-ad-spend-curve/)[### Heat pumps in Texas: ranking the new search behavior Heat pump searches in Texas grew 4× since 2023. Most Austin HVAC sites have nothing on the topic. Here's the content cluster that captures the demand. Read the guide→](/articles/heat-pump-content-texas-search-behavior/)4.9191 reviewsWhere this turns into work ## Growth you can actually see Reporting built on like-for-like periods, with the one-off events noted, so a seasonal dip never gets mistaken for a marketing problem. [See the service→](/services/marketing-automation/)[Ask us about it](/contact/) ![Leonardo Miodrag, CMO, Partner at Siite](/images/team/panel/leonardo-miodrag.webp) *Our CMO* ## Related entries - [### Google Analytics 4 Google's current analytics platform, built on events rather than pageviews, used to see where visitors came from and which pages produce calls and forms.](/dictionary/google-analytics-4/) - [### Organic Traffic Visits that arrive from unpaid search results — the traffic you earned through rankings rather than bought with ad spend.](/dictionary/organic-traffic/) - [### Average Ticket The average revenue per completed job — total revenue divided by number of jobs — used to judge whether a marketing channel is bringing the work you actually want.](/dictionary/average-ticket/) - [### Cost Per Lead What you spend to generate one inquiry — total marketing cost for a channel divided by the number of leads it produced in the same period.](/dictionary/cost-per-lead/) [All terms A to Z Browse every term A to Z Open the dictionary→](/dictionary/)